Author: Euan Dewar

Alongside the release of our Messi dataset we also put a PDF guide to using our data in R. It was intended as a basic introduction to not only our dataset but also the R programming language itself, for those who have yet to use it at any level. Hopefully that gave anyone interested in digging into football data a nice, smooth onboarding to the whole process.

For those who have taken the plunge, this article is going to go through a few more involved things that one could do with the data. This is for those that have already gone through the guide and have been playing about with SBD for a while now. It's important that you have done this first as we will not be walking through absolutely everything and assumes a certain level of familiarity with R.  Now that the base terminology of it all has been established it should be easier to explore uncharted territory with a bit less trepidation. So far we have released open data on the women’s and men’s World Cups, the FAWSL, the NWSL, Lionel Messi’s entire La Liga career, the 2003/04 Arsenal Invincibles and 15 years of Champions League finals. You can follow along with this article using any dataset you like but for consistency's sake we will be using the 2019/20 FAWSL season in all examples.

One last disclaimer: this is, of course, all about R. We also have a package for Python that isn’t quite as developed but still handles plenty of the basics for you if that’s your programming language of choice.

A big hurdle to doing anything nuanced with any dataset is one’s underlying understanding of it. There are so many distinct variables and considerations in the SB dataset that even I - having worked with it as my job for two years now - forget about some parts of it every now and then.

To this end it helps to not only have our specs to hand for checking, but also to be aware of the names() and unique() functions. These allow you to get a top-down look at the columns/rows a dataframe contains. So let’s assume you have your data in an R df called ‘events’. We will be using this name for the data in all examples throughout this article. If you were to do names(StatsBombData) that would give you a list of all the columns in your dataset.

Similarly, if you were to do unique(StatsBombData$type.name) you would get a list of every unique row that the ‘type.name’ column contains, i.e all the event types in our data. You can of course do that with any column. It’s good to have these two in your back pocket should you get lost in the forest of data at any point.

xGA, Joining and xG+xGA

xG assisted does not exist in our data initially. However, given that xGA is the xG value of a shot that a key pass/assist created, and that xG values do exist in our data, we can create xGA quite easily via joining. Here’s the code for that, we’ll go through it bit-by-bit afterwards:

library(tidyverse)
library(StatsBombR)

xGA = events %>%
filter(type.name=="Shot") %>% #1
select(shot.key_pass_id, xGA = shot.statsbomb_xg) #2
shot_assists = left_join(events, xGA, by = c("id" = "shot.key_pass_id")) %>% #3
select(team.name, player.name, player.id, type.name, pass.shot_assist, pass.goal_assist, xGA ) %>% #4
filter(pass.shot_assist==TRUE | pass.goal_assist==TRUE) #5

1. Filtering the data to just shots, as they are the only events with xG values.
2. Select() allows you to choose which columns you want to, well, select, from your data, as not all are always necessary - especially with big datasets. First we are selecting the shot.key_pass_id column, which is a variable attached to shots that is just the ID of the pass that created the shot. You can also rename columns within select() which is what we are doing with xGA = shot.statsbomb_xg. This is so that, when we join it with the passes, it already has the correct name.
3. left_join() lets you combine the columns from two different DFs by using two columns within either side of the join as reference keys. So in this example we are taking our initial DF (‘events’) and joining it with the one we just made (‘xGA’). The key is the by = c("id" = "shot.key_pass_id") part, this is saying ‘join these two DFs on instances where the id column in events matches the ‘shot.key_pass_id’ column in xGA’. So now the passes have the xG of the shots they created attached to them under the new column ‘xGA’.
4. Again selecting just the relevant columns.
5. Filtering our data down to just key passes/assists.

The end result should look like this:

All lovely. But what if you want to make a chart out of it? Say you want to combine it with xG to make a handy xG+xGA per90 chart:

player_xGA = shot_assists %>%
group_by(player.name, player.id, team.name) %>%
summarise(xGA = sum(xGA, na.rm = TRUE)) #1

player_xG = events %>% filter(type.name=="Shot") %>%
filter(shot.type.name!="Penalty" | is.na(shot.type.name)) %>%
group_by(player.name, player.id, team.name) %>%
summarise(xG = sum(shot.statsbomb_xg, na.rm = TRUE)) %>%
left_join(player_xGA) %>% mutate(xG_xGA = sum(xG+xGA, na.rm =TRUE) ) #2

player_minutes = get.minutesplayed(events)

player_minutes = player_minutes %>%
group_by(player.id) %>%
summarise(minutes = sum(MinutesPlayed)) #3

player_xG_xGA = left_join(player_xG, player_minutes) %>%
mutate(nineties = minutes/90, xG_90 = round(xG/nineties, 2),
xGA_90 = round(xGA/nineties,2),
xG_xGA90 = round(xG_xGA/nineties,2) ) #4

chart = player_xG_xGA %>%
ungroup() %>% filter(minutes>=600) %>%
top_n(n = 15, w = xG_xGA90) #5

chart<-chart %>%
select(1, 9:10)%>%
pivot_longer(-player.name, names_to = "variable", values_to = "value") %>%
filter(variable=="xG_90" | variable=="xGA_90") #6

1. Grouping by player and summing their total xGA for the season.
2. Filtering out penalties and summing each player's xG, then joining with the xGA and adding the two together to get a third combined column.
3. Getting minutes played for each player. If you went through the initial R guide you will have done this already.
4. Joining the xG/xGA to the minutes, creating the 90s and dividing each stat by the 90s to get xG per 90 etc.
5. Here we ungroup as we need the data in ungrouped form for what we're about to do. First we filter to players with a minimum of 600 minutes, just to get rid of notably small samples. Then we use top_n(). This filters your DF to the top *insert number of your choice here* based on a column you specify. So here we're filtering to the top 15 players in terms of xG90+xGA90.
6. The pivot_longer() function flattens out the data. It's easier to explain what that means if you see it first:

It has used the player.name as a reference point at creates separate rows for every variable that's left over. We then filter down to just the xG90 and xGA90 variables so now each player has a separate variable and value row for those two metrics. Now let's plot it:

ggplot(chart, aes(x =reorder(player.name, value), y = value, fill=fct_rev(variable))) + #1
geom_bar(stat="identity", colour="white")+
labs(title = "Expected Goal Contribution", subtitle = "Premier League, 2019-20",
x="", y="Per 90", caption ="Minimum 750 minutes\nNPxG = Value of shots taken (no penalties)\nxG assisted = Value of shots assisted")+
theme(axis.text.y = element_text(size=14, color="#333333", family="Source Sans Pro"),
axis.title = element_text(size=14, color="#333333", family="Source Sans Pro"),
axis.text.x = element_text(size=14, color="#333333", family="Source Sans Pro"),
axis.ticks = element_blank(),
panel.background = element_rect(fill = "white", colour = "white"),
plot.background = element_rect(fill = "white", colour ="white"),
panel.grid.major = element_blank(),
panel.grid.minor = element_blank(),
plot.title=element_text(size=24, color="#333333", family="Source Sans Pro" , face="bold"),
plot.subtitle=element_text(size=18, color="#333333", family="Source Sans Pro", face="bold"),
plot.caption=element_text(color="#333333", family="Source Sans Pro", size =10), text=element_text(family="Source Sans Pro"),
legend.title=element_blank(),
legend.text = element_text(size=14, color="#333333", family="Source Sans Pro"),
legend.position = "bottom") + #2
scale_fill_manual(values=c("#3371AC", "#DC2228"), labels = c( "xG Assisted","NPxG")) + #3
scale_y_continuous(expand = c(0, 0), limits= c(0,max(chart$value) + 0.3)) + #4
coord_flip()+ #5
guides(fill = guide_legend(reverse = TRUE)) #6

1. Two things are going on here that are different from your average bar chart. First is reorder(), which allows you reorder a variable along either axis based on a second variable. In this instance we are putting the player names on the x axis and reordering them by value - i.e the xG and xGA combined - meaning they are now in descending order from most to least combined xG+xGA. Second is that we've put the 'variable' on the bar fill. This allows us to put two separate metrics onto one bar chart and have them stack, as you will see below, by having them be separate fill colours.
2. Everything within labs() and theme() is fairly self explanatory and is just what we have used internally. You can get rid of all this if you like and change it to suit your own design tastes.
3. Here we are providing specific colour hex codes to the values (so xG = red and xGA = blue) and then labelling them so they are named correctly on the chart's legend.
4. Expand() allows you to expand the boundaries of the x or y axis, but if you set the values to (0,0) it also removes all space between the axis and the inner chart itself (if you're having a hard time envisioning that, try removing expand() and see what it looks like). Then we are setting the limits of the y axis so the longest bar on the chart isn't too close to the edge of the chart. 'max(chart$value) + 0.3' is saying 'take the max value and add 0.3 to make that the upper limit of the y axis'.
5. Flipping the x axis and y axis so we have a nice horizontal bar chart rather than a vertical one.
6. Reversing the legend so that the order of it matches up with the order of xG and xGA on the chart itself.

All in that should look like this:

Heatmaps

Heatmaps are one of the everpresents in football data. They are fairly easy to make in R once you get your head round how to do so, but can be unintuitive without having it explained to you first. For this example we're going to do a defensive heatmap, looking at how often teams make a % of their overall defensive actions in certain zones, then comparing that % vs league average:

library(tidyverse)

heatmap = events %>%
mutate(location.x = ifelse(location.x>120, 120, location.x),
location.y = ifelse(location.y>80, 80, location.y),
location.x = ifelse(location.x<0, 0, location.x),
location.y = ifelse(location.y<0, 0, location.y)) #1 

heatmap$xbin <- cut(heatmap$location.x, breaks = seq(from=0, to=120, by = 20),include.lowest=TRUE )
heatmap$ybin <- cut(heatmap$location.y, breaks = seq(from=0, to=80, by = 20),include.lowest=TRUE) #2

heatmap = heatmap%>%
filter(type.name=="Pressure" | duel.type.name=="Tackle" | type.name=="Foul Committed" | type.name=="Interception" |
type.name=="Block" ) %>%
group_by(team.name) %>%
mutate(total_DA = n()) %>%
group_by(team.name, xbin, ybin) %>%
summarise(total_DA = max(total_DA),
bin_DA = n(),
bin_pct = bin_DA/total_DA,
location.x = median(location.x),
location.y = median(location.y)) %>%
group_by(xbin, ybin) %>%
mutate(league_ave = mean(bin_pct)) %>%
group_by(team.name, xbin, ybin) %>%
mutate(diff_vs_ave = bin_pct - league_ave) #3

1. Some of the coordinates in our data sit outside the bounds of the pitch (you can see the layout of our pitch coordinates in our event spec, but it's 0-120 along the x axis and 0-80 along the y axis). This will cause issue with a heatmap and give you dodgy looking zones outside the pitch. So what we're doing here is using ifelse() to say 'if a location.x/y coordinate is outside the bounds that we want, then replace it with one that's within the boundaries. If it is not outside the bounds just leave it as is'.
2. cut() literally cuts up the data how you ask it to. Here, we're cutting along the x axis (from 0-120, again the length of our pitch according to our coordinates in the spec) and the y axis (0-80), and we're cutting them 'by' the value we feed it, in this case 20. So we're splitting it up into buckets of 20. This creates 6 buckets/zones along the x axis (120/20 = 6) and 4 along the y axis (80/20 = 4). This creates the buckets we need to plot our zones.
3. This is using those buckets to create the zones. Let's break it down bit-by-bit: - Filtering to only defensive events - Grouping by team and getting how many defensive events they made in total ( n() just counts every row that you ask it to, so here we're counting every row for every team - i.e counting every defensive event for each team) - Then we group again by team and the xbin/ybin to count how many defensive events a team has in a given bin/zone - that's what 'bin_DA = n()' is doing. 'total_DA = max(total_DA),' is just grabbing the team totals we made earlier. 'bin_pct = bin_DA/total_DA,' is dividing the two to see what percentage of a team's overall defensive events were made in a given zone. The 'location.x = median(location.x/y)' is doing what it says on the tin and getting the median coordinate for each zone. This is used later in the plotting. - Then we ungroup and mutate to find the league average for each bin, followed by grouping by team/bin again subtracting the league average in each bin from each team's % in those bins to get the difference.

Now onto the plotting. For this please install the package 'grid' if you do not have it, and load it in. You could use a package like 'ggsoccer' or 'SBPitch' for drawing the pitch, but for these purposes it's helpful to try and show you how to create your own pitch, should you want to:

library(grid)

defensiveactivitycolors <- c("#dc2429", "#dc2329", "#df272d", "#df3238", "#e14348", "#e44d51", "#e35256", "#e76266", "#e9777b", "#ec8589", "#ec898d", "#ef9195", "#ef9ea1", "#f0a6a9", "#f2abae", "#f4b9bc", "#f8d1d2", "#f9e0e2", "#f7e1e3", "#f5e2e4", "#d4d5d8", "#d1d3d8", "#cdd2d6", "#c8cdd3", "#c0c7cd", "#b9c0c8", "#b5bcc3", "#909ba5", "#8f9aa5", "#818c98", "#798590", "#697785", "#526173", "#435367", "#3a4b60", "#2e4257", "#1d3048", "#11263e", "#11273e", "#0d233a", "#020c16") #1

ggplot(data= heatmap, aes(x = location.x, y = location.y, fill = diff_vs_ave, group =diff_vs_ave)) +
geom_bin2d(binwidth = c(20, 20), position = "identity", alpha = 0.9) + #2
annotate("rect",xmin = 0, xmax = 120, ymin = 0, ymax = 80, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 0, xmax = 60, ymin = 0, ymax = 80, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 18, xmax = 0, ymin = 18, ymax = 62, fill = NA, colour = "white", size = 0.6) +
annotate("rect",xmin = 102, xmax = 120, ymin = 18, ymax = 62, fill = NA, colour = "white", size = 0.6) +
annotate("rect",xmin = 0, xmax = 6, ymin = 30, ymax = 50, fill = NA, colour = "white", size = 0.6) +
annotate("rect",xmin = 120, xmax = 114, ymin = 30, ymax = 50, fill = NA, colour = "white", size = 0.6) +
annotate("rect",xmin = 120, xmax = 120.5, ymin =36, ymax = 44, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 0, xmax = -0.5, ymin =36, ymax = 44, fill = NA, colour = "black", size = 0.6) +
annotate("segment", x = 60, xend = 60, y = -0.5, yend = 80.5, colour = "white", size = 0.6)+
annotate("segment", x = 0, xend = 0, y = 0, yend = 80, colour = "black", size = 0.6)+
annotate("segment", x = 120, xend = 120, y = 0, yend = 80, colour = "black", size = 0.6)+
theme(rect = element_blank(), line = element_blank()) +
annotate("point", x = 12 , y = 40, colour = "white", size = 1.05) + # add penalty spot right
annotate("point", x = 108 , y = 40, colour = "white", size = 1.05) +
annotate("path", colour = "white", size = 0.6, x=60+10*cos(seq(0,2*pi,length.out=2000)),
y=40+10*sin(seq(0,2*pi,length.out=2000)))+ # add centre spot
annotate("point", x = 60 , y = 40, colour = "white", size = 1.05) +
annotate("path", x=12+10*cos(seq(-0.3*pi,0.3*pi,length.out=30)), size = 0.6,
y=40+10*sin(seq(-0.3*pi,0.3*pi,length.out=30)), col="white") +
annotate("path", x=108-10*cos(seq(-0.3*pi,0.3*pi,length.out=30)), size = 0.6,
y=40-10*sin(seq(-0.3*pi,0.3*pi,length.out=30)), col="white")  + #3
theme(axis.text.x=element_blank(),
axis.title.x = element_blank(),
axis.title.y = element_blank(),
plot.caption=element_text(size=13,family="Source Sans Pro", hjust=0.5, vjust=0.5),
plot.subtitle = element_text(size = 18, family="Source Sans Pro", hjust = 0.5),
axis.text.y=element_blank(),
legend.title = element_blank(),
legend.text=element_text(size=22,family="Source Sans Pro"),
legend.key.size = unit(1.5, "cm"),
plot.title = element_text(margin = margin(r = 10, b = 10), face="bold",size = 32.5, family="Source Sans Pro", colour = "black", hjust = 0.5),
legend.direction = "vertical",
axis.ticks=element_blank(),
plot.background = element_rect(fill = "white"),strip.text.x = element_text(size=13,family="Source Sans Pro")) + #4
scale_y_reverse() + #5
scale_fill_gradientn(colours = defensiveactivitycolors, trans = "reverse", labels = scales::percent_format(accuracy = 1), limits = c(0.02, -0.02)) + #6
labs(title = "Where Do Teams Defend vs League Average?", subtitle = "FAWSL, 2019/20") + #7
coord_fixed(ratio = 95/100) + #8
annotation_custom(grob = linesGrob(arrow=arrow(type="open", ends="last", length=unit(2.55,"mm")), gp=gpar(col="black", fill=NA, lwd=2.2)), xmin=25, xmax = 95, ymin = -83, ymax = -83) + #9
facet_wrap(~team.name)+ #10
guides(fill = guide_legend(reverse = TRUE)) #11

1. These are the colours we'll be using for our heatmap later on.
2. 'geom_bin2d' is what will create the heatmap itself. We've set the binwidths to 20 as that's what we cut the pitch up into earlier along the x and y axis. Feeding 'div_vs_ave' to 'fill' and 'group' in the ggplot() will allow us to colour the heatmaps by that variable.
3. Everything up to here is what is drawing the pitch. There's a lot going on here and, rather than have it explained to you, just delete a line from it and see what disappears from the plot. Then you'll see which line is drawing the six-yard-box, which is drawing the goal etc.
4. Again more themeing. You can change this to be whatever you like to fit your aesthetic preferences.
5. Reversing the y axis so the pitch is the correct way round along that axis (0 is left in SBD coordinates, but starts out as right in ggplot).
6. Here we're setting the parameters for the fill colouring of heatmaps. First we're feeding the 'defensiveactivitycolors' we set earlier into the 'colours' parameter, 'trans = "reverse"' is there to reverse the output so red = high. 'labels = scales::percent_format(accuracy = 1)' formats the text on the legend as a percentage rather than a raw number and 'limits = c(0.03, -0.03)' sets the limits of the chart to 3%/-3% (reversed because of the previous trans = reverse).
7. Setting the title and subtitle of the chart.
8. 'coord_fixed()' allows us to set the aspect ratio of the chart to our liking. Means the chart doesn't come out looking all stretched along one of the axes.
9. This is what the grid package is used for. It's drawing the arrow across the pitches to indicate direction of play. There's multiple ways you could accomplish though, up to you how you do it.
10. 'facet_wrap()' creates separate 'facets' for your chart according to the variable you give it. Without it, we'd just be plotting every team's numbers all at once on chart. With it, we get every team on their own individual pitch.
11. Our previous trans = reverse also reverses the legend, so to get it back with the positive numbers pointing upwards we can re-reverse it.

Shot Maps

Another of the quintessential football visualisations, shot maps come in many shapes and sizes with an inconsistent overlap in design language between them. This version will attempt to give you the basics, let you get to grip with how to put one of these together so that if you want to elaborate or make any of your own changes you can explore outwards from it. Be forewarned though - the options for what makes a good, readable shot map are surprisingly small when you get into visualising it!

shots = events %>%
filter(type.name=="Shot" & (shot.type.name!="Penalty" | is.na(shot.type.name)) & player.name=="Bethany England") #1

shotmapxgcolors <- c("#192780", "#2a5d9f", "#40a7d0", "#87cdcf", "#e7f8e6", "#f4ef95", "#FDE960", "#FCDC5F", "#F5B94D", "#F0983E", "#ED8A37", "#E66424", "#D54F1B", "#DC2608", "#BF0000", "#7F0000", "#5F0000") #2

ggplot() +
annotate("rect",xmin = 0, xmax = 120, ymin = 0, ymax = 80, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 0, xmax = 60, ymin = 0, ymax = 80, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 18, xmax = 0, ymin = 18, ymax = 62, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 102, xmax = 120, ymin = 18, ymax = 62, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 0, xmax = 6, ymin = 30, ymax = 50, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 120, xmax = 114, ymin = 30, ymax = 50, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 120, xmax = 120.5, ymin =36, ymax = 44, fill = NA, colour = "black", size = 0.6) +
annotate("rect",xmin = 0, xmax = -0.5, ymin =36, ymax = 44, fill = NA, colour = "black", size = 0.6) +
annotate("segment", x = 60, xend = 60, y = -0.5, yend = 80.5, colour = "black", size = 0.6)+
annotate("segment", x = 0, xend = 0, y = 0, yend = 80, colour = "black", size = 0.6)+
annotate("segment", x = 120, xend = 120, y = 0, yend = 80, colour = "black", size = 0.6)+
theme(rect = element_blank(), line = element_blank()) + # add penalty spot right
annotate("point", x = 108 , y = 40, colour = "black", size = 1.05) +
annotate("path", colour = "black", size = 0.6, x=60+10*cos(seq(0,2*pi,length.out=2000)),
y=40+10*sin(seq(0,2*pi,length.out=2000)))+ # add centre spot
annotate("point", x = 60 , y = 40, colour = "black", size = 1.05) +
annotate("path", x=12+10*cos(seq(-0.3*pi,0.3*pi,length.out=30)), size = 0.6,
y=40+10*sin(seq(-0.3*pi,0.3*pi,length.out=30)), col="black") +
annotate("path", x=107.84-10*cos(seq(-0.3*pi,0.3*pi,length.out=30)), size = 0.6,
y=40-10*sin(seq(-0.3*pi,0.3*pi,length.out=30)), col="black") +
geom_point(data = shots, aes(x = location.x, y = location.y, fill = shot.statsbomb_xg, shape = shot.body_part.name), size = 6, alpha = 0.8) + #3
theme(axis.text.x=element_blank(),
axis.title.x = element_blank(),
axis.title.y = element_blank(),
plot.caption=element_text(size=13,family="Source Sans Pro", hjust=0.5, vjust=0.5),
plot.subtitle = element_text(size = 18, family="Source Sans Pro", hjust = 0.5),
axis.text.y=element_blank(), legend.position = "top",
legend.title=element_text(size=22,family="Source Sans Pro"),
legend.text=element_text(size=20,family="Source Sans Pro"),
legend.margin = margin(c(20, 10, -85, 50)),
legend.key.size = unit(1.5, "cm"),
plot.title = element_text(margin = margin(r = 10, b = 10), face="bold",size = 32.5, family="Source Sans Pro", colour = "black", hjust = 0.5),
legend.direction = "horizontal",
axis.ticks=element_blank(), aspect.ratio = c(65/100),
plot.background = element_rect(fill = "white"), strip.text.x = element_text(size=13,family="Source Sans Pro")) +
labs(title = "Beth England, Shot Map", subtitle = "FAWSL, 2019/20") + #4
scale_fill_gradientn(colours = shotmapxgcolors, limit = c(0,0.8), oob=scales::squish, name = "Expected Goals Value") + #5
scale_shape_manual(values = c("Head" = 21, "Right Foot" = 23, "Left Foot" = 24), name ="") + #6
guides(fill = guide_colourbar(title.position = "top"),  shape = guide_legend(override.aes = list(size = 7, fill = "black"))) + #7 coord_flip(xlim = c(85, 125)) #8

1. Simple filtering, leaving out penalties. Choose any player you like of course.
2. Much like the defensive activity colours earlier, these will set the colours for our xG values.
3. Here's where the actual plotting of shots comes in, via geom_point. We're using the the xG values as the fill and the body part for the shape of the points. This could reasonably be anything though. You could even add in colour parameters which would change the colour of the outline of the shape.
4. Again titling. This can be done dynamically so that it changes according to the player/season etc but we will leave that for now. Feel free to explore for youself though.
5. Same as last time but worth pointing out that 'name' allows you to change the title of a legend from within the gradient setting.
6. Setting the shapes for each body part name. The shape numbers correspond to ggplot's pre-set shapes. The shapes numbered 21 and up are the ones which have inner colouring (controlled by fill) and outline colouring (controlled by colour) so that's why those have been chosen here. oob=scales::squish takes any values that are outside the bounds of our limits and squishes them within them.
7. guides() allows you to alter the legends for shape, fill and so on. Here we are changing the the title position for the fill so that it is positioned above the legend, as well as changing the size and colour of the shape symbols on that legend.
8. coord_flip() does what it says on the tin - switches the x and y axes. xlim allows us to set boundaries for the x axis so that we can show only a certain part of the pitch, giving us:

That's all for now. Hopefully this wasn't all too confusing and you picked up some bits and bobs you can take away to play with yourselves. Don't worry if some of this is overwhelming or you have to do copious amounts of googling to overcome odd specific errors and whatnot. That's just part and parcel with coding (seriously, get used to googling for errors, everyone has to).

Much love. Be well and have great days.

To define our terms upfront: a successful dribble in this context is when a player with possession of the ball takes it past an opponent. This is the definition that Opta uses, as well as sites like Squawka and Whoscored that present Opta’s data.

'Dribbles’/’Take-Ons’/whatever your football website of choice calls them are an odd stat in isolation. We can probably assume that a player who completes a lot dribbles is of a certain stylistic mould. Other than that though, there isn’t a lot to be learnt from those raw numbers about where these dribbles take place, where they go and what the players do afterwards.

To illustrate the point let’s compare two players: Manchester City’s Leroy Sané and Huddersfield’s Rajiv van La Parra. Both are wingers who play predominantly on the left and complete a bit over 3 dribbles per 90 in similar minutes (Sané at a 63.5% completion rate overall and La Parra at 53.5%). Their base stats are very similar, however if we map out where those dribbles start/end and the actions they follow them up with we can see a difference.

La Parra is often starting from deeper areas - he has attempted near the most dribbles starting in his own half of any player in the top 5 leagues -  and ends up going inwards surprisingly frequently (most of his completed passes are received by their strikers or other attackers). His post-dribble work, especially in more traditional winger areas, isn’t great. However he does win his share of fouls and generally advances his team up the pitch. Sané, meanwhile, is operating in the opposition’s third and a whole hell of a lot in that cutback area his manager Guardiola loves. He’s already in such a dangerous area to begin with that the simple act of just beating his man is hugely concerning for the opposition to deal with. The rest is just the icing on the cake.

Obviously there is complexity wrapped around all this. Huddersfield are a world away from Man City, especially in terms of wider squad quality. Different players are needed to bring different qualities to different situations. La Parra needs to beat his man in order to help his team’s progression. Sané, who on average receives the ball already in the final third, needs to beat his man in order help his team break down deep blocks. Po-tay-to po-tah-to.

Below are the top players in terms of their dribble and post-dribble numbers entering and within the opposition box (all stats per 90 for the 2017/18 season. This dataset is missing a couple of Ligue 1 matches). There are clear standouts here: Messi is eye-watering (he already has more post-dribble box passes/shots in 17/18 than in the entirety of 16/17. At 30-years-old!), the Premier League names you'd expect are all there, Leon Bailey is having a lovely season for himself, so on and so forth.

We can zoom out further, to take a look at involvement in possessions that go on to reach the opposition's final 18 yards (both via a dribble or a post-dribble pass), along with a player’s own individual entries to those areas. The added value from the dribbling of someone like a Hazard, a Boufal or whomever is obvious here. The final ball is the eye-catcher but offering a means of progression is important too.

The focus shouldn’t be on just pure attackers though. The list below shows involvement in possessions that end in the opposition's final third, filtered to players whose median dribble location is outside the final third. Sort by percentage of these dribbles that come through the centre (within the width of the penalty boxes, minimum 30 possessions involved in) and this is where some real atypical profiles come up. E.g: Mousa Dembélé. A main point of consternation for Tottenham right now is what the team will look like without Dembélé. He's an attacking midfielder turned central midfielder with the ability to move with the ball like an AM in congested areas while also holding up as a defensive presence. His dribbles don’t always directly lead to the final third, but they help the team eventually get there (and this has even been a slight down season by his standards).

It's a difficult skill set to replace. Do you try to re-train a younger AM like Dembélé himself was? 20-year-old Amine Harit (who just misses out on this list) at Schalke could fit the bill, with similar dribbling tendencies. Or do you go for someone who is doing a similar job at CM elsewhere? Southampton's Mario Lemina is one of those, and a growing favourite candidate amongst supporters. Outside of the PL there's Tanguy Ndombele who is doing a stellar job in a messily structured Lyon team. He had 10(!) dribbles against Rennes at the weekend.

The list of prospective replacements could go on but the point is that, while there’s players who rack up more eye-popping dribbling numbers than Dembélé, the type of dribble he’s executing combined with his efficacy is maddeningly rare.

Of course none of this is to knock the dribbles stat entirely, or to say it’s without use. Statsbomb’s own radars use them in what seems like the ideal way: present it alongside the rest of a player’s numbers so as to give an at-a-glance impression of their general ability and style. If two players have high Key Pass numbers but one completes a lot of dribbles and the other doesn’t, that tells you a fair amount right there. 

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That's all for right now though. Maybe we'll expand on this and have more fun with it in the future. Thank you for reading. You can find me on Twitter @EuanDewar.

In just a scant few days the La Liga teams will return from their truncated winter rest. Before we dive head first into the home straight of the season, let's take a look back at what the first chunk of games has taught us, shall we? This isn't technically the halfway-point as Spain's domestic break comes after 17 games rather than 19. Don't worry though, we're not about to let that get in the way of a good ol' rummage through the numbers!

Valencia

From 2013 to 2016 Villarreal had a pretty successful run of seasons under then manager Marcelino, culminating in achieving Champions League qualification and reaching the Europa League semifinals in 2015/16. That summer - before they had even played their CL qualification match - vague tensions between Marcelino and the club’s higher-ups lead to him getting the sack out of nowhere. He took a sabbatical for the 2016/17 season and now is back in La Liga, taking charge of Valencia. At this stage they sit 3rd in the table with the 2nd best goal difference. After chewing through five managers in two seasons, Los Che appear to have found their man.

Marcelino’s Villarreal built their success on a rock-solid defensive 4-4-2 shape, somewhat like a more reserved version of Diego Simeone’s Atlético Madrid. In his final season they ranked 3rd in terms of expected goals against and a pretty uninspiring 17th in terms of attacking xG. At Valencia things appear the same on the surface - the 4-4-2 is in use again - but the attack/defence split has been shaken up somewhat unexpectedly.

Functionally the attack is, again, closer to an Atléti than a Barca. Meaning that getting the ball forward with pace is the order of the day. They're just about middle of the pack in terms of possessions that are 10 or more passes in length. Conversely, they have the fourth highest percentage of their possessions leading to shots that are 15 seconds or shorter. This continues a trend from Mareclino's last season at Villarreal where they lead the league in this measure. However, in Valencia, the efficacy is greatly improved with them getting far more shots overall from these situations.

While the attack is clearly humming, a word of caution: it's perhaps running a tad too hot. They're over-shooting their expected goals numbers right now and come season's end may fall back behind Real Madrid to about 3rd or 4th in terms of goals scored (unless this bizarre Real Madrid finishing slump just continues in perpetuity). Simone Zaza - who has genuinely been quite good this season after a couple of odd detours in his career - is the one to point to here. Regardless, things are encouraging.

Defensively there a couple of slight causes for concern. The relatively high amount of shots they're giving up isn't necessarily a problem as long as the quality of said shots is as low as it has been (45% of their shots conceded are from outside the box, the 2nd highest percentage in the league). However, it is a bit easier to move the ball against them than Marcelino would probably ideally like. Opposition possessions are reaching Valencia's defensive third at the 5th highest rate in the league. On top of that they're not doing especially well at keeping opponents out of the most dangerous areas. The xG says don't stress it but it's worth keeping an eye on.

Marcelino's boys likely aren't, as the early results have suggested, on a level with Barca and Real Madrid. However, the signs do point towards them being the league's third best, even beyond an Atléti (more on them later). That is plenty impressive on its own.

Girona

Gironaaaaaaaaaaaaaa!...

...are the surprise package in La Liga this season. Prior to this campaign most probably knew them as the destination for a lot of Manchester City's loan army (about a third of Girona's squad are loanees, five of which are from City). That doesn't define them though, they're a hoot in their own right. The newly promoted club sit 9th in the table at this point of the season, and look just as good - if not a bit better - in the underlying indicators.

Manager Pablo Machín has them at a high level of defensive organisation all over the pitch. As you may have seen above, they allow one of the lower proportions of opposition completions in the final 18 yards, pointing towards a sturdy shape near to their own goal. They engage pretty high up the pitch too, forcing the 6th lowest completion percentage on passes originating in the opponent's defensive third along with the 4th lowest proportion of opposition possessions that are 'long' (10 or more passes). Put this all together and you see them keeping opponents out of their third at a super impressive rate.

On the other side of the ball there's two big defining stylistic points: 1) they've gotten the joint most goals from set pieces in the league (9) - a route of value you'll hear reiterated time and time again on this here website, especially for promoted teams - and 2) they love a headed shot, racking up the 2nd most of those, with the 2nd highest proportion of their completed passes into the opposition box coming via crosses. Other than that, there's no one regard in which their attack sticks out. They just do a little bit of everything. Long possessions per game? Middle of the pack. Counter-attacking situations? Solid there too. Shots from turnovers in opposition's third? They do them quite well. You get the gist.

Lots of players deserve praise here but the most eye-catching has been 20-year-old right-back Pablo Maffeo. The City loanee has shown real creativity going forward as a wing-back and generally just a nice all-round game, handling himself very well in marking assignments on bloody Lionel Messi and Cristiano Ronaldo. Opponents complete their passes in his zone (the right side of Girona's defensive third) at the 3rd lowest rate in the league. He looks ready to slot in back at City, should Guardiola see fit to do so.

Someone might want to talk to him about the shots though. Oy vey.

Atlético Madrid

On the face of it there's little wrong with Atlético Madrid this season. They currently sit 2nd in the table, only having just suffered their first league loss of the campaign in the final match before the break. Everything hunky dory then? Well, peer below the surface and things start to look a tad iffy.

The defence is still looking about par but the attack has dropped off to a quite alarming extent. It's like Marcelino has sapped all the offensive capability out of Madrid and directly into his Valencia team.

41% of their shots came from outside the box last season, that’s up to a league-leading 47% this time around. The root of this appears to be in their transition game. Atléti's deep and compact defensive shape is the yin that require's a counter-attacking yang. Otherwise you're just defending all the time. Right now, they're struggling to get out.

On top of that, the shots they're getting from turnovers in the opposition's third is down by about half a shot per game. Possibly most troubling of all is that they've only managed 3 goals all season from set pieces, one of the worst tallies in the league. Something that was previously their bread and butter. All in it's a dual issue of both shot volume and quality. Even Antoine Griezmann, whose individual volume is about the same as last season on a per 90 basis, isn't producing a great deal.

They've certainly improved their passing game over the years, to the point where now they're about average in how many shots they squeeze out of possessions that last 10 passes or longer. That'd be A-OK if everything else were working normally but it just isn't. With the points banked already maybe it won't be such a big deal. Simeone's obviously a fantastic manager and he might potentially cure what ails them. And of course the impending return of Dastardly Diego Costa will be a boon. If it doesn't turn around though, and the results don't keep going their way, it could be an underwhelming first season in the new stadium. __________________

Thanks for reading. You can find me @EuanDewar for any questions or the like. Enjoy the rest of the season!

The idea behind shot quality in football is really a fairly intuitive one. A shot from the halfway line isn’t as good an idea as a shot from inside the six-yard box. There’s more nuance to it but you don’t need any sort of deep analytical education to grasp it. Hell, it’s right there in why goals like this one from Memphis are so memorable: because we don’t expect them to happen.

Yet, in spite of this, shot quality and the improvement of it feels like a bit of an uphill battle. Especially when it comes to coaching the idea into younger players who have a particularly frustrating problem with their shot selection (Hakim Ziyech, bij voorbeeld). However, it would appear that, one way or another, teams are starting to pay real attention to their shot selection. I noticed this while compiling some shots numbers and tweeted about it, prompting the ever lovely Colin Trainor to produce this nice summary:

Shots are being taken from closer to goal in recent seasons. Seems teams are appreciating shot quality more. Prompted by @EuanDewar's tweet. pic.twitter.com/AP5Uvf3dFv

— Colin Trainor (@colintrainor) May 28, 2017

Whether you talk about it in terms of shot distance or shot zones, teams across Europe’s top five leagues are cutting the fat off of their shots. This article is going to focus on the Premier League specifically, mainly because there’s just so many things to digest across Europe that this could go on forever, so a cutoff point has to be set somewhere. If you want details on what's going elsewhere give me a bell on twitter and if there's enough curiosity there might be a follow up. 

(*distance numbers for 16/17 are a few matches out of date, but you get the gist)

The first thing that sticks out is the relationship between shots taken outside the box and the total shots numbers. Bits are getting shaved off the outside numbers with each passing season, yet those shots aren’t really being replaced with anything. However, this isn’t really ending up as a loss in end product because of the increased focus on better shots.  Everything is floating around in similar totals, and the goals aren't going away that's for sure.

(If you’re wondering about the slight increase in distance in 13/14 that season was very, very odd in an attacking sense. There were 184 goals scored from outside the box that season, 22 more goals than the next highest total over the last five seasons. Most of those were Luis Suarez scoring against Norwich. Or at least that’s what it felt like).

Which teams then are embracing this change and leading the charge in these numbers?

Arsenal put up the lowest % from outside the box in the recently finished 2016/17 season with an exceedingly low 33.03%. This makes sense for a couple of reasons. Firstly it fits with the image of them of as the English Barcelona, building their attack around getting high value shots (by the by, Barca’s % of shots outside the box in 16/17 was 31.9%). You may also remember that in late 2014 they bought StatsDNA, an analytics company. Now, obviously it’s hard to tell from the outside how much sway they have, but Wenger has mentioned things like expected goals in the past so it seems quite likely that the sharp dropoff between the 14/15 to 15/16 season is at least partially down to StatsDNA being in the discussion and Wenger being open to what they have to say.

In that 15/16 season they absolutely crushed it on the attacking end. It was the ne plus ultra of ‘they always try to walk it in’. Their average shot distance that season was the lowest of any team over the last 5 seasons. This saw their xG per shot jump from 0.105 in 2014/15 to 0.125 which, again, was the highest of any team over that timeframe. This season they’ve become more dysfunctional in attack but that’s a whole other story entirely.

Their North London neighbours Tottenham are another interesting case. Plenty has been said about how Mauricio Pochettino seems to emphasise long range shots as a part of his gameplan, and sure enough his Tottenham sides have a similarly high % from outside the box as his Southampton one. Yet even though they had the highest % overall in the 16/17 season he has still actually brought the number down from where it was before he took over. It appears that AVB was even more content for his players to take pot shots than Pochettino is. Bless his soul.

Another big (and perhaps unexpected) contributor to the overall league dropoff is your friend and mine Sam Allardyce. West Ham under Allardyce from 2012 to 2015 were always posting low %s, and then as soon as he leaves and Slaven Billic takes over those numbers shoot up. Sure enough in his lone season at Palace they had a similarly low average. His time at Sunderland is the outlier, but it seems none of the many managers they’ve gone through have been able to greatly change their numbers. Much was made from early on in Allardyce's career about how he embraced stats and let it shape how he worked. Billic meanwhile seems to prefer the volume over quality approach.

Funnily enough there's another manager who has this effect: the Right Honourable Tony Pulis.

Allardyce and Pulis doing this shows that it's the idea of shot location that matters, not how you achieve it. They aren't bringing down their teams' average shot distances with intricate play and sly throughballs like an Arsenal or a Man City are. They're adapting the idea to the strengths of their players, utilising more headers and the like. An equally valid way of reaching the same end result.

And that's the point of all this: teams are getting the message on shot locations and starting to remove some of the more pointless shots out of their attacking diet. Will long shots ever go away? No, nor should they. Everyone loves a thunderbastard goal from outside the box. The aim here isn't to turn every team into a Poundland version of Barcelona. It's just to make them a little bit smarter and to maximise what they get out of their attack.