I often work with ggplot2
that makes gradients nice (click here for an example). I have a need to work in base and I think scales
can be used there to create color gradients as well but I'm severely off the mark on how. The basic goal is generate a palette of n colors that ranges from x color to y color. The solution needs to work in base though. This was a starting point but there's no place to input an n.
scale_colour_gradientn(colours=c("red", "blue"))
I am well aware of:
brewer.pal(8, "Spectral")
from RColorBrewer
. I'm looking more for the approach similar to how ggplot2
handles gradients that says I have these two colors and I want 15 colors along the way. How can I do that?
The above answer is useful but in graphs, it is difficult to distinguish between darker gradients of black. One alternative I found is to use gradients of gray colors as follows
palette(gray.colors(10, 0.9, 0.4))
plot(rep(1,10),col=1:10,pch=19,cex=3))
More info on gray scale here.
Added
When I used the code above for different colours like blue and black, the gradients were not that clear.
heat.colors()
seems more useful.
This document has more detailed information and options. pdf
Just to expand on the previous answer colorRampPalette
can handle more than two colors.
So for a more expanded "heat map" type look you can....
colfunc<-colorRampPalette(c("red","yellow","springgreen","royalblue"))
plot(rep(1,50),col=(colfunc(50)), pch=19,cex=2)
The resulting image:
Source: Stackoverflow.com