[R] Color intervals in image function (image.plot)

[David Winsemius]

On Feb 8, 2010, at 12:06 PM, FMH wrote:

> Hi,
>
> The script below is my current coding in order to produce a contour  
> plot of temperature across altitude and time. In my case,  
> time,altitude and temperature are represented by x, y and z variables.
>
>
> ##############################################
> Brazilan.Pallete <- colorRampPalette(c("blue","green","yellow","red"))
> image.plot(x, y, z, col = Brazilan.Pallete(50))
> contour(x,y,z, levels = seq(1, 20, by = 1), add = TRUE, col = 'peru')
> ##############################################
>
>
>
> The plot worked fine but i found difficult to fix the interval of  
> the color corresponding to z value. In my case, the range of z  
> values is between 1 and 40 and  i'd like to fix the color in the  
> image correspoding to four sub-intervals of z values. For instance:
>
> 1. 1 < z < 10 : blue
> 2. 11 < z < 20: green
> 3. 21 < z < 30: yellow
> 4. 31 < z < 40 : red.
>
> I did't find a suitable coding to do this. Could someone please give  
> an advice on this matter?

Have you tried setting the number of colors in the palette to 40, and  
the levels in image.plot at seq(1, 40, by=2). Wouldn't that get the  
transitions and the contour lines to line up correctly at color  
transitions?

>
> Thank you.
> Fir
>
>
>
>
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT