Advanced R

13

Non-standard evaluation

“Flexibility in syntax, if it does not lead to ambiguity, would seem a reasonable thing to ask of an interactive programming language.”

— Kent Pitman

R has powerful tools for computing not only on values, but also on the actions that lead to those values. If you’re coming from another programming language, they are one of the most surprising features of R. Consider the following simple snippet of code that plots a sine curve:

x <- seq(0, 2 * pi, length = 100)

sinx <- sin(x)

plot(x, sinx, type = "l")

Look at the labels on the axes. How did R know that the variable on the x axis is called x and the variable on the ...