I am trying to emulate e.g. the following base graphic in ggplot2 (for constructing calibrated biplot axes):
## Base graphics
plot(-1:1, -1:1, asp = 1, type = "n", xaxt = "n", yaxt = "n", xlab = "", ylab = "")
abline(a = 0, b = -0.75)
abline(a = 0, b = 0.25)
abline(a = 0, b = 2)
mtext("V1", side = 4, at = -0.75*par("usr")[2])
mtext("V2", side = 2, at = 0.25*par("usr")[1])
mtext("V3", side = 3, at = par("usr")[4]/2)
The calls to mtext() adds the variable names to the plot margin and indicates the positive directions of the respective axes.
However, there does not seem to be a ggplot2 equivalent to the mtext() function of base graphics. Hence I have not been able to figure out how to put the variable names in the margin of the plot. Does anyone have ideas on how to do this?
Preferably I would not want to disable clipping. Here are some equivalent code for a ggplot2 version of the above:
## ggplot2 attempt
library(ggplot2)
df <- data.frame(x = -1:1, y = -1:1)
dfLabs <- data.frame(x = c(1, -1, 1/2), y = c(-0.75, -0.25, 1), labels = paste0("V", 1:3))
p <- ggplot(data = df, aes(x = x, y = y)) + geom_blank() +
geom_abline(intercept = rep(0, 3), slope = c(-0.75, 0.25, 2)) +
theme_bw() + coord_cartesian(xlim = c(-1, 1), ylim = c(-1, 1)) +
theme(axis.title = element_blank(), axis.text = element_blank(), axis.ticks = element_blank(),
panel.grid = element_blank())
p + geom_text(data = dfLabs, mapping = aes(label = labels))
The geom_text() call in the last line have to be modified.
