如何绘制填充轮廓，z轴是一个因素

Question

I have a dataset

test<-data.frame(expand.grid(x=seq(0.01,1,0.01), y=seq(0.01,1,0.01)))
test$z<-c(rep(1,2500),rep(2,2500),rep(3,2500),rep(4,2500))

(x,y) define cartesian coordinates. I would like to plot a filled contour plot, with xlim=ylim=c(0,1) , and the color being z (a factor with 4 levels).

i could do :

plot(test$x, test$y, col=test$z, pch=16) but it does not look good.

The example looks terrible but in my data makes sense. I am familiar with akima::interp and filled.contour() but i do not wish any interpolation and z is not continuous but a factor.

Could you please recommend me a proper and pleasant visualization for my data? I would prefer base graphics.

Answer 1

You can use image for example :

image(outer(seq(0.01,1,0.01),seq(0.01,1,0.01),
            FUN=function(x,y)test$z))

I think you can use raster package to deal better with such plots.