reverse colors in colorNumeric()

Question

I am trying to reverse the colors of a choropleth map. I am using the leaflet package and the colorNumeric() function, here is the code that generates the palette function:

pal <- colorNumeric(palette = "YlGnBu", domain = foo$p)

I would like to do something like that:

pal <- colorNumeric(palette = "YlGnBu", domain = foo$p, trans='reverse')

Does anyone knows how to do this?

Possible duplicate of [How to reverse order a vector?](http://stackoverflow.com/questions/18933441/how-to-reverse-order-a-vector) — Jota, Jul 06 '16 at 16:33
I do not think that it is clear for everyone that a color palette is a vector. Hence, I wouldn't call it a duplicate of the above mentioned. — Alex, Jul 06 '16 at 17:37

Alex · Accepted Answer · 2016-07-06T16:39:29.277

10

Without an example I cannot tell if it works with your code but try this:

library(RColorBrewer)
palette <- brewer.pal(5, "YlGnBu")
previewColors(colorNumeric(palette = palette, domain = 1:5), values = 1:5)

And the reverse:

palette_rev <- rev(brewer.pal(5, "YlGnBu"))
previewColors(colorNumeric(palette = palette_rev ,domain = 1:5), values = 1:5)

edited Jul 06 '16 at 16:39

answered Jul 06 '16 at 16:30

Alex

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score 9 · Answer 2 · answered Jun 07 '17 at 09:14

9

At least in leaflet 1.1.0+ colorNumeric has an optional "reverse" argument, so you can just do:

pal <- colorNumeric(palette = "YlGnBu", domain = foo$p, reverse = TRUE)

answered Jun 07 '17 at 09:14

Stefan F

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TimSalabim · Answer 3 · 2016-07-06T17:19:05.863

1

As suggested by @Alex here's an example using rev with some actual data:

library(leaflet)
library(mapview)
library(RColorBrewer)

clrs <- rev(brewer.pal(9, "YlGnBu"))

pal <- colorNumeric(palette = clrs, domain = poppendorf[[5]][])

m <- leaflet() %>% addTiles() 

m %>% 
  addRasterImage(x = poppendorf[[5]], color = pal)

edited Jul 06 '16 at 17:19

answered Jul 06 '16 at 16:35

TimSalabim

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No offence intended! You must have provided your answer while I was still trying and typing my answer... I've edited mine to acknowledge yours. – TimSalabim Jul 06 '16 at 17:20

reverse colors in colorNumeric()

3 Answers3