heatmap

Andrea Zangrando wrote:
 > Hi,
 > i created a graph with heatmap(sma) function:
 >
 > heatmap(dataHeat(x))
 >
 > and I wish to change the gradation of colors from blue to red, how could
 > i do?
 > Using "heatmap(dataHeat(x), col=c(2,4))" i will use only 2 colors
 > without gradation.
 >
The color.gradient function in the plotrix package returns a sequence of 
interpolated colors between any two starting colors or incomplete 
sequences of primaries.

I noticed that a function named ramp (in the base package?) was 
mentioned, but I could not find it. If there is a function equivalent to 
color.gradient, I would like to know about it, as I try to avoid 
duplicating functions.
see ?colorRamp and look at:
colorRampPalette
function (colors, ...) 
{
    ramp <- colorRamp(colors, ...)
    function(n) {
        x <- ramp(seq(0, 1, length = n))
        rgb(x[, 1], x[, 2], x[, 3], max = 255)
    }
}

to see where it comes from. The colorRamp/colorRampPalette combination is 
quite remarkable and lots of fun ...

Roger
Jim

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Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
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e-mail: Roger.Bivand at nhh.no

heatmap

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