Can dplyr package be used for conditional mutating?

Question

Can the mutate be used when the mutation is conditional (depending on the values of certain column values)?

This example helps showing what I mean.

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Answer 1

The derivedFactor function from mosaic package seems to be designed to handle this. Using this example, it would look like:

library(dplyr)
library(mosaic)
df <- mutate(df, g = derivedFactor(
     "2" = (a == 2 | a == 5 | a == 7 | (a == 1 & b == 4)),
     "3" = (a == 0 | a == 1 | a == 4 | a == 3 |  c == 4),
     .method = "first",
     .default = NA
     ))

(If you want the result to be numeric instead of a factor, you can wrap derivedFactor in an as.numeric call.)

derivedFactor can be used for an arbitrary number of conditionals, too.