axis labels - pROC ROC curves remove empty space

Question

I want to draw ROC curves with pRoC. However for some reason there is extra empty space on either side of the x-axis and I cannot remove it with xlim. Some example code:

library(pROC)
n = c(4, 3, 5) 
b = c(TRUE, FALSE, TRUE) 
df = data.frame(n, b) 
rocobj <- plot.roc(df$b, df$n, percent = TRUE, main="ROC", col="#1c61b6", add=FALSE)

I tried the pROC help file, but that doesn't really help me. Even more puzzling is to me that the Y-axis is OK looking...

I really appreciate your help!

Answer 1

Make sure the plotting device is square and adjust the margins so that top + bottom == left + right:

library(pROC)
png("test.png", width = 480, height = 480)
par(mar = c(4, 4, 4, 4)+.1)
n = c(4, 3, 5) 
b = c(TRUE, FALSE, TRUE)
rocobj <- plot.roc(b, n, percent = TRUE, main="ROC", col="#1c61b6", add=FALSE)
dev.off()