I need a gradient function for two "sides", let me explain:
Example:
x <- c(1,4,3,4,5,6,1,8,9,3)
then I need a array of color, the number 5 is the main color blue and the smaller and larger numbers are the gradient to red.
I found this
colorRampPalette(c("red", "blue"))
but if I do:
colfunc <- colorRampPalette(c("red", "blue"))
colfunc(10)
Returns a color progression from red to blue ignoring the value...
How can I do this?
Ps: I don't use any library...
For share with the community,
using the function "colorRampPalette", like:
col <- colorRampPalette(c('red', 'blue','red'))(10)[y]
where 10 is the range 1:10 with extremities red and in middle (5) in blue and other values are the gradient going to red.
in an example,
size <- 30 #number of value in the data vector
x <- c(1:size)
y <- c(1 ,2 ,3.5,3 ,4,
5 ,5.5,6 ,6.3,7,
5 ,2 ,1 ,0.5,1.6,
2.3,5.7,6 ,7 ,7.5,
8 ,9 ,11 ,12 ,10,
7 ,6.4,5 ,4.6 ,4)
col <- colorRampPalette(c('red', 'blue','red'))(12)[y]
plot(x, y) # draw the points, in black
for (i in 1:size-1) # draw the segments in colour
lines(x[i:(i+1)], y[i:(i+1)], type='o', pch=16, col=col[i])
