[R] adjusting color palette

[Barry Rowlingson]

Laura Quinn wrote:
> Is there a way to increase the "sensitivity" of the color palette in order
> to more clearly represent certain sections of data? For example I am
> wanting to clearly differentiate between height data for a rolling
> landscape but because of the extremes of the dataset (sea and mountain
> tops), the bulk of the landscape is shaded in closely approximating green
> - i have attempted to do this by using a larger color palette but this
> doesn't make things any clearer.

  The colour is selected linearly by the value you are drawing. Hence 
two solutions present themselves:

  one, non-linearly scale your data. for your application I think 
squaring x-mean(x) might stretch out the tails.

  two, constructing a non-linearly varying palette. you can do this by 
mucking about with the red, green, and blue values from the palette.

  the functions 'col2rgb' and 'rgb' are useful.

  Baz