How to recognize automatically a formula in R?

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Let's assume the following data.frame

d <- data.frame(x = 1:10, y = 11:20)

Let's now assume that some user input, leads to the following variable

z <- "x + 0.25 * y"

where z is a character, but intended to be interpreted as a formula.

d$z <- d$x + 0.25 * d$y

For regression, the conversion is straightforward with as.formula(), but here I want it to apply to a DF column. The gas-factory method would be to split and identify each separator and translate them.

r
1 Answers

We can use eval and use the environment of 'd'

eval(parse(text = z), d)
#[1]  3.75  5.00  6.25  7.50  8.75 10.00 11.25 12.50 13.75 15.00
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