Question

I have a plot that has $-amounts and dates on y and x axis respectively. Currently the dollar amounts range from $0-15 million. Something like this:

x <- rnorm(20)^2 * 1000000
plot(x)

R does stuff like '1.0e+07' instead of '10,000,000' and also orients the text vertically instead of horizontally.

My questions are:

1) how would I get the scale text to be horizontally oriented?

2) how would I get R to use 10MM instead of '10,000,000' or '1.0e+07'?

Answer 1

1) See the scipen option in ?options which is a penalty against the use of scientific notation. For better control, you need to plot the axis by hand with labels you want.

2) See las in ?par which controls to orientation crudely of axis labels.

For 1):

x <- rnorm(20)^2 * 10000000
layout(matrix(1:2, ncol = 2))
plot(x)
getOption("scipen")
opt <- options("scipen" = 20)
getOption("scipen")
plot(x)
options(opt)
layout(1)

which gives

To plot your own axis try

plot(x / 10000000, axes = FALSE)
axis(1)
pts <- pretty(x / 10000000)
axis(2, at = pts, labels = paste(pts, "MM", sep = ""))
box()

Which gives

Where we use pretty() to select pretty locations for the ticks just as R would and then add a custom axis. Notice how we suppress axis drawing in the plot() call and then add back the axes and the plot frame with calls to axis() and box().

For 2) combining with 1)

opt <- options("scipen" = 20)
op <- par(mar = c(5,7,4,2) + 0.1) ## extra margin to accommodate tick labs
x <- rnorm(20)^2 * 10000000
plot(x, las = 1, ylab = "")       ## no y-axis label 
title(ylab = "label", line = 5.5) ## need to plot the axis label
par(op)
options(opt)

Which gives

Notice how we use las in the plot() call, and we need to create some extra margin space to accommodate the tick labels. We also need to plot the label by hand otherwise R will stick it in amongst the tick labels.

For the custom axis labels, add the las = 1 to the axis() call:

op <- par(mar = c(5,5,4,2) + 0.1)
plot(x / 10000000, axes = FALSE, ylab = "")
axis(1)
pts <- pretty(x / 10000000)
axis(2, at = pts, labels = paste(pts, "MM", sep = ""), las = 1)
title(ylab = "my label", line = 4)
box()
par(op)

Which produces