Heat map soccer game in r - r

Question

I have a dataframe with the position of a player on a pitch.
The bounding box for the area is 0 - 1000 and 0 - 750.
The starting ball position is 375-500 and the starting player position is 637-692.
I was trying using geom_tile but I can't get a heat map. How can I link the variables to make a heatmap?
frames <- structure(list(half = c("1T", "1T", "1T", "1T", "1T", "1T", "1T",
"1T", "1T", "1T", "1T", "1T", "1T", "1T", "1T", "1T", "1T", "1T",
"1T", "1T", "2T", "2T", "2T", "2T"), `ball-X` = c(375L, 375L,
375L, 375L, 375L, 372L, 365L, 358L, 351L, 344L, 338L, 332L, 326L,
320L, 315L, 310L, 305L, 301L, 300L, 309L, 631L, 631L, 631L, 631L
), `ball-Y` = c(500L, 500L, 500L, 500L, 500L, 490L, 470L, 450L,
432L, 414L, 397L, 381L, 365L, 350L, 336L, 322L, 309L, 297L, 302L,
304L, 577L, 582L, 589L, 596L), `L-2-X` = c(637L, 637L, 636L,
636L, 639L, 639L, 641L, 643L, 645L, 648L, 652L, 656L, 660L, 665L,
669L, 672L, 673L, 674L, 673L, 672L, 227L, 230L, 233L, 235L),
`L-2-Y` = c(692L, 692L, 691L, 688L, 685L, 684L, 681L, 678L,
674L, 669L, 663L, 657L, 649L, 641L, 633L, 624L, 615L, 606L,
596L, 587L, 438L, 445L, 452L, 460L)), class = "data.frame", row.names = c(NA,
-24L))
ggplot(frames, aes(x = `L-2-X`, y = `L-2-Y`)) +
scale_x_continuous(limits = c(0,750))+
scale_y_continuous(limits = c(0,1000))+
geom_tile(aes(fill = `L-2-X`)) +
scale_fill_viridis_c(option = "B", direction = -1) +
theme_light()+
facet_grid(~ half)

Answer 1

Not sure about the final result you are trying to achieve. As far as I get it your code works fine. However, your tiles are simply to small for being visible. Only when I zoomed the plot some tiny tiles appeared.
Therefore I would recommend to bin the data to get a nice heatmap. As an example my code below bins the data in squares of size 25 to 25 (cm??). For the fill I simply count the number of obs per square. Another approach would be to use e.g. geom_hex which uses hexagons for the binning.
library(ggplot2)
library(dplyr)
# Bin data
frames_bin <- frames %>%
# Bin data
mutate(l_2_x = cut(`L-2-X`, breaks = seq(0, 750, 25), labels = seq(0, 725, 25), include.lowest = TRUE),
l_2_y = cut(`L-2-Y`, breaks = seq(0, 1000, 25), labels = seq(0, 975, 25), include.lowest = TRUE)) %>%
# Count number of obs per bin
count(half, l_2_x, l_2_y) %>%
# Convert factors to numeric
mutate_at(vars(l_2_x, l_2_y), ~ as.numeric(as.character(.x)))
ggplot(frames_bin) +
scale_x_continuous(limits = c(0, 750)) +
scale_y_continuous(limits = c(0, 1000)) +
geom_tile(aes(x = l_2_x, y = l_2_y, fill = n)) +
scale_fill_viridis_c(option = "B", direction = -1) +
theme_light()+
facet_grid(~ half)
# Out of the box: use geom_hex
ggplot(frames) +
scale_x_continuous(limits = c(0, 750)) +
scale_y_continuous(limits = c(0, 1000)) +
geom_hex(aes(x = `L-2-X`, y = `L-2-Y`, fill = ..ncount..)) +
scale_fill_viridis_c(option = "B", direction = -1) +
theme_light()+
facet_grid(~ half)