On 20/11/2010 8:53 AM, Jason Rupert wrote:
In the following example I would like to have the color transition from
Red->yellow->green in the image(...) function, and if possible have the yellow
be set to correspond with the mean value (for the below 75).
You can get the colour transition using the colorRamp or
colorRampPalette functions. For example, to get 12 colours from red
through yellow to green, use
colorRampPalette(c("red", "yellow", "green"), space="Lab")(12)
This will put yellow in the middle of the range. If the mean isn't in
the middle, you'll need something a little more complicated involving
colorRamp. It returns a function mapping the numbers 0 to 1 into the
colours you specify; you'll need to write your own function that maps
(min, mean, max) to (0, 0.5, 1) in some way.
Duncan Murdoch
I was able to figure something like out when using filled.contour(...), e.g.
filled.contour(ak.fan, levels = c(70, 73, 76, 80, 90), color = terrain.colors)
(I still couldn't get the Red->yellow->green transition figured out for this
example...ugh...need more caffeine)
I am hoping a similar amount of control is available using image:
library(akima)
hyp_distance<-seq(1,15)
angle_deg_val<-seq(0,15)
x_distance_val<-NULL
y_distance_val<-NULL
for(ii in 1:length(hyp_distance))
{
for(jj in 1:length(angle_deg_val))
{
x_distance_tmp<-hyp_distance[ii]*cos(angle_deg_val[jj]*pi/180)
y_distance_tmp<-hyp_distance[ii]*sin(angle_deg_val[jj]*pi/180)
x_distance_val<-c(x_distance_val, x_distance_tmp)
y_distance_val<-c(y_distance_val, y_distance_tmp)
}
}
temperature_vals<-rnorm(length(x_distance_val), 75, 2.2)
temp_samples<-cbind(x_distance_val, y_distance_val, temperature_vals)
ak.fan<- interp(temp_samples[,1],temp_samples[,2],temp_samples[,3] )
filled.contour(ak.fan, levels = c(70, 73, 76, 80, 90), color = terrain.colors)
image(ak.fan)
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and provide commented, minimal, self-contained, reproducible code.
