color number

[saisaitian]

Dear authuors：

when I use ggsci， the scale_color_npg() only provied 10 colors，in fact ，I need 15 colors，how can I fix it?

[nanxstats]

Good question. Automatic color palette extrapolation is a doable feature and has been planned for ggsci 3.0.0. In case I don't have time to work on that this year, here is how it can be done by yourself:

library("ggsci")

#' Adaptive palette (discrete).
#'
#' Create a discrete palette which will use the first n colors from
#' the supplied color values, and interpolate after n.
adaptive_pal <- function(values) {
  force(values)
  function(n = 10) {
    if (n <= length(values)) {
      values[seq_len(n)]
    } else {
      colorRampPalette(values, alpha = TRUE)(n)
    }
  }
}

pal_npg_adaptive <- function(palette = c("nrc"), alpha = 1) {
  palette <- match.arg(palette)
  
  if (alpha > 1L | alpha <= 0L) stop("alpha must be in (0, 1]")
  
  raw_cols <- ggsci:::ggsci_db$"npg"[[palette]]
  raw_cols_rgb <- col2rgb(raw_cols)
  alpha_cols <- rgb(
    raw_cols_rgb[1L, ], raw_cols_rgb[2L, ], raw_cols_rgb[3L, ],
    alpha = alpha * 255L, names = names(raw_cols),
    maxColorValue = 255L
  )
  
  adaptive_pal(unname(alpha_cols))
}

scale_color_npg_adaptive <- function(palette = c("nrc"), alpha = 1, ...) {
  palette <- match.arg(palette)
  discrete_scale("colour", "npg", pal_npg_adaptive(palette, alpha), ...)
}

scale_fill_npg_adaptive <- function(palette = c("nrc"), alpha = 1, ...) {
  palette <- match.arg(palette)
  discrete_scale("fill", "npg", pal_npg_adaptive(palette, alpha), ...)
}

library("ggplot2")

dsamp <- diamonds[sample(nrow(diamonds), 1000), ]
dsamp$table <- as.factor(dsamp$table)

ggplot(dsamp, aes(carat, price)) + geom_point(aes(colour = table)) +
  theme_bw() + scale_color_npg_adaptive()

[saisaitian]

where is discrete_scale function? could you provide?

[nanxstats]

@saisaitian https://ggplot2.tidyverse.org/reference/discrete_scale.html

[albert-ying]

Nice function! Will it ever be integrated into the ggsci package? I mean, since you already have the function here

[nanxstats]

I posted a more generic version of the above code here: https://nanx.me/blog/post/ggplot2-color-interpolation/

I will also look into the possibility to incorporate this into the package in future releases.

[zhouyutong123]

Nice function! But how to adjust the order of colors after using the above function?

[nanxstats]

@zhouyutong123 I guess the main purpose of this is automation. While you can always use any additional logic to adjust the colors (including ordering) in pal_adaptive(), or simply create a manual color scale and adjust there: https://r-graphics.org/recipe-colors-palette-discrete-manual

[nanxstats]

Fixed by https://github.com/nanxstats/ggsci/commit/78a24cea89c994cc1ee6fd1f7fcb3109e1c376f7