R/helper_funs.R

In densityarea: Polygons of Bivariate Density Distributions

# unexported functions from ggplot and ggdensity

isoband_z_matrix <- function(data) {
  # Convert vector of data to raster
  x_pos <- as.integer(factor(data$x, levels = sort(unique(data$x))))
  y_pos <- as.integer(factor(data$y, levels = sort(unique(data$y))))

  nrow <- max(y_pos)
  ncol <- max(x_pos)

  raster <- matrix(NA_real_, nrow = nrow, ncol = ncol)
  raster[cbind(y_pos, x_pos)] <- data$z

  raster
}

xyz_to_isolines <- function(data, breaks) {
  isoband::isolines(
    x = sort(unique(data$x)),
    y = sort(unique(data$y)),
    z = isoband_z_matrix(data),
    levels = breaks[-length(breaks)]
  )
}