Question

Is there a shorter way to select elements and modify them? For example, in

y[y < 1] <- y[y < 1]*2

the object y is referenced 4 times in one line. Is it possible to reduce this repetition?

Answer 1

Here’s a construct that reduces the number of references to y by 1:

y <- -2:2
y[i] <- y[i <- y < 1] * 10

y
# [1] -20 -10   0   1   2

In practice, though, I’m more likely to do this, which is maybe less “clever” but is certainly much easier to parse (for a human):

i <- y < 2
y[i] <- y[i] * 10