dplyr mutate with conditional values

Question

In a large dataframe (\"myfile\") with four columns I have to add a fifth column with values conditionally based on the first four columns.

Prefer answers with

Answer 1

It looks like derivedFactor from the mosaic package was designed for this. In this example, it would look something like:

library(mosaic)
myfile <- mutate(myfile, V5 = derivedFactor(
    "1" = (V1==1 & V2!=4),
    "2" = (V2==4 & V3!=1),
    .method = "first",
    .default = 0
    ))

(If you want the outcome to be numeric instead of a factor, wrap the derivedFactor with an as.numeric.)

Note that the .default option combined with .method = "first" sets the "else" condition -- this approach is described in the help file for derivedFactor.