Example · R

A quickly made cake graph

Since square pie graphs have been found to be very good for judging proportions as reported here and seen by me here, I have sketched out some quick code for making square pie graphs, that I really feel should be called cake graphs.

cakegraph <- function(labls, values, colours=1:length(values), leg=TRUE) {
 if (leg==FALSE){
 plot(c(0,.1), c(0,1), type="n", axes=FALSE, xlab="", ylab="")
 }
 if (leg==TRUE){
 plot(c(0,.15), c(0,1), type="n", axes=FALSE, xlab="", ylab="")
 }
 upperx <- cumsum(values/sum(values))
 lowerx <- c(0, upperx[1:length(upperx)-1])
 plotdata <- data.frame(lowerx, upperx, colours)
 #by rows
 rowseq <- seq(from=0, to=.9, by= 0.1)
 for(arow in rowseq){
 rowdata <- plotdata[plotdata$lowerx < arow + 0.1 & plotdata$upperx > arow, ]
 rowdata$lowerx[rowdata$lowerx < arow] <- arow
 rowdata$upperx[rowdata$upperx > arow + 0.1] <- arow + 0.1
 for (eachentry in 1:length(rowdata)){
 x1 <- rowdata$lowerx[eachentry]-arow
 x2 <- rowdata$upperx[eachentry]-arow
 x3 <- rowdata$lowerx[eachentry]-arow
 x4 <- rowdata$upperx[eachentry]-arow
 y1 <- arow
 y2 <- arow
 y3 <- arow + 0.1
 y4 <- arow + 0.1
 polygon(c(x1,x2,x4,x3), c(y1,y2,y3,y4), col=rowdata$colours[eachentry], border=rowdata$colours[eachentry])
 }
 }
 if (leg==TRUE){
 legend(.105,1, legend=rev(paste(labls, " (",values,")", sep="")), fill=rev(colours), bty="n", y.intersp=1.4, cex=0.9)
 }
}

data(mtcars)
mtb <- table(mtcars$cyl)
cakegraph(names(mtb), mtb)

Looking at the example this code makes,

I am not convinced it is easier to read than a bar graph for multiple proportions, particularly with custom tick marks at the bar heights.

cakegraph

I would also note that if you want binned coloured boxes (so have some rounding of the data) you should be looking at the waffle package.

The cakegraph function is on github at:

https://github.com/thoughtfulbloke/cakegraph

 

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