R devel - Jan 2003 - proposal: lattice/panel.levelplot with show.z.values

I suggest to add an argument to levelplot
which displays the z values in the cells.

In the special case of a correlogram the correlation values could
be rotated by 45 degres when the correlation is positive and by
-45 degress when the correlation is negative (see example).

Wolfram

NB: The same code should be to panel.catlevelplot if this panel
function will be implemented.


#---- ADDITIONAL ARGUMENTS FOR panel.levelplot() -------------------

	show.z.values = FALSE,		# display z values in the cells
								# if -1:  if( srt == 0 ) srt <- 45
								#         if( z < 0 )  srt <- -srt
	cex			= 1,			# size of z values
	signif		= 2,			# number of significant digits of z values
	srt			= 0,			# rotation of z values


#---- ADDITIONAL CODE AT THE END OF panel.levelplot() --------------

		if( show.z.values ){
			if( show.z.values < 0 )
				srt <- ifelse( srt==0, 45, srt ) * sign( z[subscripts] )
			ltext(
				  x = x[subscripts]
				, y = y[subscripts]
				, labels = signif( z[subscripts], signif )
				, cex = cex
				, srt = srt
				)
		}

#---- EXAMPLE ------------------------------------------------------

library(EMV)
data(swiss)
example.corplot.swiss <- function( show.z.values=-1, ... ){
	x.cor <- cor( knn( as.matrix( swiss ) )$data )
	diag( x.cor ) <- 0
	x.names <- colnames( swiss )
	x.cor.data	<- data.frame(
		  x		= rep( x.names, length( x.names ) )
		, y		= rep( x.names, each=length( x.names ) )
		, val	= as.vector( x.cor )
		)
	print( levelplot( val ~ x + y, data = x.cor.data
		, show.z.values = show.z.values
        , scales= list(
              x = list( labels = x.names, rot=90, alternating=F
                  , at = 1 : length( x.names ) )
            , y = list( labels = x.names, alternating=F
                  , at = 1 : length( x.names ) )
            )
        , zlim  = c( -1, 1 )
        , ...
		))
}