How to change color scheme in corrplot

Question

I am using corrplot in R to visualise a correlation-coefficient matrix as follows.

library(corrplot) 
library(datasets)
corrplot(abs(cor(mtcars)), method="color", tl.pos="n", cl.lim = c(0,1))

The default colour scheme is blue-based. However, I would like to change it to red-based. I know I need to use colorRampPalette to specify colours I want. However, I could not figure out what colour codes to use. Could anyone help me with this, please?

Thank you!

Answer 1

The function colorRampPalette returns a function that takes a numeric argument:

corrplot(abs(cor(mtcars)), method="color",
         col= colorRampPalette(c("white","pink", "red"))(10) ,
         tl.pos="n", cl.lim = c(0,1))

The default is defined with this color spectrum:

col2 <- colorRampPalette(c("#67001F", "#B2182B", "#D6604D", "#F4A582", "#FDDBC7",
        "#FFFFFF", "#D1E5F0", "#92C5DE", "#4393C3", "#2166AC", "#053061"))  

This would give you a wider range of reds:

colnew <- colorRampPalette(c("#670000", "#B20000", "#D60000", "#F40000", "#FD0000", "#FFFFFF"))

And I thought adding a "brown" at the end extended the range for better visual separation:

col= colorRampPalette(c("white","lightpink", "red","brown"))(10)

Answer 2

If you want to use red, you can define your own colorRampPalette as you've alread mentioned. Just note that the plot seems to set the range of colors from -1 to 1 (even if you adjust the cl.lim value). Thus you still need to define colors for the -1 to 0 range in your ramp. For example

corrplot(abs(cor(mtcars)), method="color", tl.pos="n", 
    cl.lim=c(0,1), col=colorRampPalette(c("blue","white","red"))(200))

will produce

and even though we defined "blue" in the color palette, it doesn't show up because we limited the color bar to values greater than 1.

This "unused" part of the color gradient cab be seen with the original version as well if you take out cl.lim

corrplot(abs(cor(mtcars)), method="color", tl.pos="n")