4.PlotingShots.md

Plotting Shots Using Statsbomb Data

In the previous tutorial we learnt how to create a plot map background for use with Statsbomb data. Let's use what we learn and then plot some shots for one particular game.

Before We Start

If you have not done so already check out:

1. Getting Started With StatsBomb Data
2. Creating a Statsbomb Ready Shot Map with ggplot2

The Setup

We need to turn off warnings and load the ggplot2 and dplyr packages.

options(warn=-1)
require(ggplot2); require(dplyr)

## Loading required package: ggplot2

## Loading required package: dplyr

## 
## Attaching package: 'dplyr'

## The following objects are masked from 'package:stats':
## 
##     filter, lag

## The following objects are masked from 'package:base':
## 
##     intersect, setdiff, setequal, union

Create The Base Shot Map

Let's recreate the function that we created in our previous tutorial.

create_StatsBomb_ShotMap <- function(grass_colour, line_colour, background_colour, goal_colour){
  
  theme_blankPitch = function(size=12) { 
    theme(
      #axis.line=element_blank(), 
      axis.text.x=element_blank(), 
      axis.text.y=element_blank(), 
      #axis.ticks.y=element_text(size=size),
      #   axis.ticks=element_blank(),
      axis.ticks.length=unit(0, "lines"), 
      #axis.ticks.margin=unit(0, "lines"), 
      axis.title.x=element_blank(), 
      axis.title.y=element_blank(), 
      legend.background=element_rect(fill=background_colour, colour=NA), 
      legend.key=element_rect(colour=background_colour,fill=background_colour), 
      legend.key.size=unit(1.2, "lines"), 
      legend.text=element_text(size=size), 
      legend.title=element_text(size=size, face="bold",hjust=0),
      strip.background = element_rect(colour = background_colour, fill = background_colour, size = .5),
      panel.background=element_rect(fill=background_colour,colour=background_colour), 
      #       panel.border=element_blank(), 
      panel.grid.major=element_blank(), 
      panel.grid.minor=element_blank(), 
      panel.spacing=element_blank(), 
      plot.background=element_blank(), 
      plot.margin=unit(c(0, 0, 0, 0), "lines"), 
      plot.title=element_text(size=size*1.2), 
      strip.text.y=element_text(colour=background_colour,size=size,angle=270),
      strip.text.x=element_text(size=size*1))}
  
    ymin <- 0 # minimum width
    ymax <- 80 # maximum width
    xmin <- 60 # minimum length
    xmax <- 120 # maximum length
    
    # Defining features along the length
    boxEdgeOff <- 102
    sixYardOff <- 114
    penSpotOff <- 108
    halfwayline <- 60
    
    # Defining features along the width
    boxEdgeLeft <- 18
    boxEdgeRight <- 62
    sixYardLeft <- 30 
    sixYardRight <- 50
    goalPostLeft <- 36
    goalPostRight <- 44
    CentreSpot <- 40   
    
    # other dimensions
    centreCirle_d <- 20   
  
  ## define the circle function
  circleFun <- function(center = c(0,0),diameter = 1, npoints = 100){
    r = diameter / 2
    tt <- seq(0,2*pi,length.out = npoints)
    xx <- center[1] + r * cos(tt)
    yy <- center[2] + r * sin(tt)
    return(data.frame(x = xx, y = yy))
  }

  #### create leftD arc ####
  dArc <- circleFun(c((40),(penSpotOff)),centreCirle_d,npoints = 1000)
  ## remove part that is in the box
  dArc <- dArc[which(dArc$y <= (boxEdgeOff)),]
    
    ## initiate the plot, set some boundries to the plot
  p <- ggplot() + xlim(c(ymin,ymax)) + ylim(c(xmin,xmax)) +
  # add the theme 
  theme_blankPitch() +
  # add the base rectangle of the pitch 
  geom_rect(aes(xmin=ymin, xmax=ymax, ymin=xmin, ymax=xmax), fill = grass_colour, colour = line_colour) +
  # add the 18 yard box offensive
  geom_rect(aes(xmin=boxEdgeLeft, xmax=boxEdgeRight, ymin=boxEdgeOff, ymax=xmax), fill = grass_colour, colour = line_colour) +
  # add the six yard box offensive
  geom_rect(aes(xmin=sixYardLeft, xmax=sixYardRight, ymin=sixYardOff, ymax=xmax), fill = grass_colour, colour = line_colour) +
  # add the arc circle 
  geom_path(data=dArc, aes(x=x,y=y), colour = line_colour) +
     # add the goal offensive
  geom_segment(aes(x = goalPostLeft, y = xmax, xend = goalPostRight, yend = xmax),colour = goal_colour, size = 1)
  
  return(p)

}

## plot the base shot map 
p <- create_StatsBomb_ShotMap("#ffffff", "#A9A9A9", "#ffffff", "#000000")
p

Now we have a base map let's plot the shots of one team, to do this we need to wrangle some data.

Creating the data we need

First we load in our saved events DB

events <- readRDS("SB_events_DB.RDS")

Now we are going to use the power of the dplyr package to trim the data down to just the shots of one team from one match.

dat <- events %>% filter(match_id == "7443" & team.name == "Portland Thorns FC" & type.name == "Shot")
## add a goal count to help plotting
dat$Goal <- ifelse(dat$shot.outcome.name == "Goal","1","0")

Plotting the Shots

Basic Version

p + geom_point(data = dat, aes(x=location.y, y=location.x), colour = "#DF5058")

Goal Outcomes Version

p + geom_point(data = dat, aes(x=location.y, y=location.x, colour = Goal)) +
  theme(legend.position="none") + 
  scale_colour_manual(values = c("#F1BEBE", "#DF5058"))

xG and Goal Outcomes Version

p + geom_point(data = dat, aes(x=location.y, y=location.x, size=shot.statsbomb_xg, colour = Goal)) + 
  theme(legend.position="none") + 
  scale_colour_manual(values = c("#F1BEBE", "#DF5058"))

Titles, Totals, xG and Goal Outcomes Version

p + geom_point(data = dat, aes(x=location.y, y=location.x, size=shot.statsbomb_xg, colour = Goal)) + 
  theme(legend.position="none") + 
  scale_colour_manual(values = c("#F1BEBE", "#DF5058")) + 
  geom_text(aes(x = 2, y=68,label = dat$team.name[1]), hjust=0, vjust=0.5, size = 5, colour = "#DF5058") +
  geom_text(aes(x = 2, y=66,label = paste0("Expected Goals (xG): ",round(sum(dat$shot.statsbomb_xg),2))), hjust=0, vjust=0.5, size = 3) + 
  geom_text(aes(x = 2, y=64,label = paste0("Actual Goals: ",round(sum(as.numeric(dat$Goal)),0))), hjust=0, vjust=0.5, size = 3) + 
    geom_text(aes(x = 2, y=62,label = paste0("xG Difference: ",round(sum(as.numeric(dat$Goal)),0)-round(sum(dat$shot.statsbomb_xg),2))), hjust=0, vjust=0.5, size = 3)