Hi ALL, How can I differentiate the area that does not have data or the data is below the minimum value using color when I plot Contour chart. For example, my data value range is from 5.0 to 7.5, but I am interested in the data value from 5.5 to 7.5, so I change levels in the quant2plot variable. How ever, I want to differentiate the area between NO data and data value below 5.5. My script is attached as below, please advise me to implement this function. Thanks in advance! z<-data.matrix(read.table('c:/3029197.txt',sep=',')) x<-1:nrow(z) y<-1:ncol(z) SameVal<-0 quant2plot<-c(5.5,5.9,6,6.165,6.29,6.39,6.524,6.9568,7.5) windows(width=5.5,height=3.5) par(mar=c(2.3,2.8,2,5),cex.main=1,cex.axis=0.7,cex.lab=1) filled.contour(x,y,z, levels=quant2plot, key.axes=axis(4,quant2plot), col=c('#8888ff','#00ff70','#00ff00','#afff00','#ffff00','#ffd700','#ffa000','#ff0000'), plot.title=title(main='My Title') ) Best Regards, WeiQiang Li [[alternative HTML version deleted]]