I have been trying to change the fillstyle for the filledcurves option so that the fill colour represents the difference between the two curves on a 2-dimensional plot. I am thinking of this as an extension of the 'filledcurves above/below' option whereby instead of just having two colours representing above or below there is a colour range or palette.
Here is an example of the plot I would like to make from a datafile using the above/below filled curve style http://i.stack.imgur.com/RLlpU.png A colourbar representing the y-difference between the two curves would be very useful - an example plot of a filledcurve with a color map is attached.
I have tried to do this by adding a fourth column to the using command i.e.
plot 'data.txt' using 1:2:3:($3-$2) with filledcurves fs palette
but the filledcurves does not appear to accept the fourth column... I have also considered trying rgb variable but this doesn't seem to work either.