R: index-based apply to vector-CodePudding

Given:

original_vector <- c(2, 2, 2, 3)
indices <- c(1, 0, 0, 1)

I want to apply some function to original_vector, but based on indices. e.g. if the function is "increment by 5", my desired output would be [7, 2, 2, 8].

I know how do this with a for-loop but I'd like to use something in the apply family.

There are similar questions, but they seem to be more complicated than my own usecase.

CodePudding user response：

If you want to use something from the apply family, consider mapply and provide both vectors. mapply and the custom function my_fun are taking two arguments: original_vector and indices.

my_fun <- function(vec, indices) {
  vec[indices == 1] <- vec[indices == 1]   5
  vec
}

mapply(my_fun, original_vector, indices)

Output

[1] 7 2 2 8

CodePudding user response：

In dplyr you can do this:

library(dplyr)
data.frame(original_vector, indices) %>%
  mutate(original_vector = ifelse(indices > 0,
                                  original_vector   5,
                                  original_vector))
  original_vector indices
1               7       1
2               2       0
3               2       0
4               8       1