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Animating Tracking Data

Source: vignettes/animating-tracking-data.Rmd
animating-tracking-data.Rmd

For the following vignette, you’ll need the sportyR, ggplot2, and gganimate packages loaded into your workspace.

library(sportyR)
library(ggplot2)
library(gganimate)
#> No renderer backend detected. gganimate will default to writing frames to separate files
#> Consider installing:
#> - the `gifski` package for gif output
#> - the `av` package for video output
#> and restarting the R session

If this is your first experience with plotting tracking data, please check out the plotting-tracking-data vignette. Otherwise, let’s see how to make GIFs with sportyR and gganimate.

The Data

For this example, we’ll use a play from Week 15 of the 2018 NFL season between the Chicago Bears and Green Bay Packers. Data made available for the Big Data Bowl 2021 Kaggle competition.

# Load the play data
example_nfl_play <- data.table::fread(
  glue::glue(
    "https://raw.githubusercontent.com/sportsdataverse/sportyR/",
    "main/data-raw/example-pbp-data.csv"
  )
)

# Convert to data frame
example_nfl_play <- as.data.frame(example_nfl_play)

To keep things easy, let’s specify the colors for each team’s dots on the resulting GIF. We’ll make the Bears orange and the Packers yellow. The football will also need a dot to be seen; let’s make it brown.

# Prep data for plotting
example_nfl_play[example_nfl_play["team"] == "home", "color"] <- "#c83803"
example_nfl_play[example_nfl_play["team"] == "away", "color"] <- "#ffb612"
example_nfl_play[example_nfl_play["team"] == "football", "color"] <- "#624a2e"

First, let’s draw an NFL field via geom_football("nfl"). We’ll adjust the origin to be in the lower left corner of the field, as per the notes on the coordinate system on the Kaggle page describing the data.

# Create the field
nfl_field <- geom_football("nfl", x_trans = 60, y_trans = 26.6667)

# Display the field
nfl_field

Image of NFL field rendered from sportyR

Looks good! Now, let’s animate using gganimate.

# Add the points on the field
play_anim <- nfl_field +
  geom_point(
    data = example_nfl_play,
    aes(x, y),
    color = example_nfl_play$color
  ) +
  transition_time(example_nfl_play$frameId)

# Show the animation
play_anim

Gif of tracking data

Easy peasy. As noted on the plotting-tracking-data vignette, this too works so long as the geospatial data is provided and contains a way to identify and order the frames of the resulting GIF.