<3

hrt.R

require(lattice)

hrt <- function(x, y) {
  x^2 + (y-(x^2)^(1/3))^2
}

hrt_mat <- matrix(10000, nrow=100, ncol=100)
x_vals <- seq(-1, 1, length.out=100)
y_vals <- seq(-1, 1.5, length.out=100)
for (x in seq(1:nrow(hrt_mat))) {
  for (y in seq(1:ncol(hrt_mat))) {
    hrt_mat[x, y] <- hrt(x_vals[x], y_vals[y])
  }
}

hrt_cols <- colorRampPalette(c("darkred", "pink"))


levelplot(hrt_mat, pretty=TRUE, col.regions=hrt_cols(150), colorkey=FALSE)

library(rgl)

cols_3d <- hrt_cols(length(hrt_mat_m$value))
hrt_mat_m <- hrt_mat_m[order(hrt_mat_m$value), ]
hrt_mat_m$cols_3d <- cols_3d
plot3d(hrt_mat_m$Var1, hrt_mat_m$Var2, hrt_mat_m$value, col=hrt_mat_m$cols_3d)