Get contour lines — get_contours • genevoisgame

Get contour lines, using a wrapper for contourLines

get_contours(df = NULL, levels = 0, ...)

Arguments

df	A data.frame containing x, y, and z columns. x and y must form a raster, meaning every x must be represented for each y, and vice versa.
levels	A vector of values at which contours should be plotted. If used, nlevels is ignored.
...	If x, y, and z are directly specified here, df will be ignored.

Examples

library(ggplot2)

df <- expand.grid(x=-10:10,y=-10:10)
df$z <- df$x^2
cl <- get_contours(df,levels=5)
unique(cl$level)
#> [1] 5
ggplot() +
  geom_raster(data=df,aes(x,y,fill=z)) +
  geom_path(data=cl,aes(x,y,group=line))

cl <- get_contours(df,levels=c(15,20,60))
unique(cl$level)
#> [1] 15 20 60

df <- expand.grid(x=seq(-5,5,length.out=20),y=seq(-5,5,length.out=20))
df$z <- sqrt(df$x^2+df$y^2)
cl <- get_contours(df,levels=seq(2,10,by=2))
ggplot() +
  geom_raster(data=df,aes(x,y,fill=z)) +
  geom_path(data=cl,aes(x,y,group=line)) + coord_equal()