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Convert Soccer Event Coordinates to the sdvplotR Pitch Frame

Source: R/pitch_coords.R
sdv_pitch_coords.Rd

Every soccer data provider uses its own coordinate frame. Opta and Wyscout run 0-100 on both axes and are not to scale, StatsBomb uses 120 x 80, tracking providers use meters or centimeters from the center spot, and ESPN reports the distance from the attacked goal as a fraction of half the pitch. sdv_pitch_coords() converts any of them to one frame: meters, origin at the center spot, a regulation 105 x 68 m pitch, attacking toward +x, with +y on the attacker's left. That is the pitch sdv_surface() draws for "soccer".

Usage

sdv_pitch_coords(
  data,
  provider,
  x_column = NULL,
  y_column = NULL,
  flip = NULL,
  pitch_length = NULL,
  pitch_width = NULL
)

Arguments

data

A data frame of events.

provider

The coordinate frame of data: "opta" (alias "statsperform"), "wyscout", "statsbomb", "uefa", "impect", "espn", "tracab", "skillcorner", "secondspectrum" or "metrica". Case is ignored.

x_column, y_column

Strings naming the coordinate columns. NULL (the default) uses the provider's usual names: "field_position_x" and "field_position_y" for ESPN (the output of Python espn_soccer_game_plays()), "x" and "y" otherwise.

flip

NULL (no row flipped), TRUE/FALSE for every row, or a string naming a logical column with no missing values; TRUE rows are turned half a turn.

pitch_length, pitch_width

The venue's size in meters, for tracking providers only (the Laws of the Game allow 90-120 by 45-90).

Value

data with pitch_x and pitch_y added (existing columns of those names are replaced); every other input column is kept as-is:

col_nametypedescription
pitch_xnumericMeters along the pitch: -52.5 is the defended goal line, 52.5 the attacked one, 0 the halfway line
pitch_ynumericMeters across the pitch: -34 to 34; positive = the attacker's left

Details

The conversion is piecewise-linear between pitch landmarks: goal line, six-yard line, penalty spot, box edge and halfway line along the pitch; touchline, box side, six-yard side and post across it. A shot on the edge of an Opta box therefore lands on the edge of the regulation box, not 1.35 m outside it as a linear rescale would put it. Points beyond the outermost landmark are extrapolated from the nearest segment, not clamped. The landmark values come from 'mplsoccer' and ship in system.file("extdata", "pitch_landmarks.csv", package = "sdvplotR").

Tracking providers ("tracab", "skillcorner", "secondspectrum", "metrica") are measured on the venue's real pitch, so they need pitch_length and pitch_width. ESPN frames are derived from the Opta frame: opta_x = 100 - 50 * x and opta_y = 100 * (1 - y). ESPN marks an event with no location as (0, 0), which becomes NA.

Event providers record every action as if the team attacked left to right. To draw two teams (or two halves of tracking data) attacking opposite ends, flip them: a flipped row is turned half a turn, so its x and y both change sign and each wing stays on its own side.

See also

sdv_surface() draws the pitch; ggsoccer::rescale_coordinates() converts between provider frames without the regulation-pitch output.

Examples

shots <- data.frame(x = c(88.5, 83, 50), y = c(50, 21.1, 100))
sdv_pitch_coords(shots, "opta")
#>      x     y pitch_x pitch_y
#> 1 88.5  50.0    41.5    0.00
#> 2 83.0  21.1    36.0  -20.16
#> 3 50.0 100.0     0.0   34.00

# two teams attacking opposite ends
shots$away <- c(FALSE, TRUE, FALSE)
sdv_pitch_coords(shots, "opta", flip = "away")
#>      x     y  away pitch_x pitch_y
#> 1 88.5  50.0 FALSE    41.5    0.00
#> 2 83.0  21.1  TRUE   -36.0   20.16
#> 3 50.0 100.0 FALSE     0.0   34.00

# tracking data, measured on the venue's pitch
tracking <- data.frame(x = c(-4150, 3600), y = c(0, -2016))
sdv_pitch_coords(tracking, "tracab", pitch_length = 105, pitch_width = 68)
#>       x     y pitch_x       pitch_y
#> 1 -4150     0   -41.5  1.776357e-15
#> 2  3600 -2016    36.0 -2.016000e+01