Hello,

I have a question on sp package.

I drew pixel heat maps of continental U.S. using insurance litigation data.
If an insurance claim is litigated at a certain location, 1 is assigned;
otherwise 0 is assigned. I have assigned a value between 0 and 1 to each
pixel on my map using inverse-distance weighting (spatial smoothing).

I need to draw two pixel maps, one for period 2001-2006 and the other for
period 2007-2010, to gauge the impacts of regulation changes in certain
states. However, the same probability (eg. 10%) is mapped to two different
colors in two plots, making the maps incomparable. So the mapping from data
to colors is determined by the range of the data?

Is it possible to fix the color mapping (from value to color) in advance,
so that the two heat maps will share not only the same palette but also the
same mapping?

color palette: rbs <- rainbow(100, start=.5, end=1)

X <- spplot(idw.out['litigated'],
            sp.layout=list('sp.polygons',STATE_SPL, first=FALSE),
            *col.regions=rbs*,
            main=list(label=expression( atop('Claim Litigation',
                atop(italic('notice date 2001 - 2006') ) )), cex=3),
            xlab = list('industry = construction', cex=2, col='blue') )

Thank you!

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