R + d3.js for interpolating colors in LAB

I spotted this blog post about interpolating colors in LAB with d3.js. Since I think the scales package in R doesn’t get the attention it deserves, I wanted to replicate the example in R.

in R with scales

# do d3 interpolateLab in R with scales
# https://translate.google.com/translate?hl=en&sl=ja&tl=en&u=http%3A%2F%2Fblog.aagata.ciao.jp%2F%3Feid%3D116

library(scales)
plot(
  0:10,
  col=col_numeric(
    palette=c("white","steelblue"),
    domain=c(0,10)
  )(0:10),
  pch=16,cex=2
)

plot(
  0:10,
  col=col_numeric(
    palette=c("blue","red"),
    domain=c(0,10)
  )(0:10),
  pch=16,cex=2
)

use R V8 to get same colors from d3

To extend the theme of parallel R and JavaScript examples (see yesterday’s nesting and summarizing example), I’ll add a bonus example using V8 to get the colors in R but using d3.js.

# for fun get colors from d3 using V8
#  using same code as http://blog.aagata.ciao.jp/?eid=116
library(V8)
ctx <- v8()
ctx$source("https://d3js.org/d3.v3.min.js")
ctx$eval(
  '
  //http://blog.aagata.ciao.jp/?eid=116
  var cscale = d3.scale
    .linear()
    .domain([0, 10])
    .range(["blue", "red"])
    .interpolate(d3.interpolateLab);

  var colors = d3.range(0,10).map(function(d){return cscale(d)});
  '
)
colors <- ctx$get("colors")
plot(1:10, col=colors, pch=16, cex=2)