How to use custom functions in mutate (dplyr)?

Question

I\'m rewriting all my code using dplyr, and need help with mutate / mutate_at function. All I need is to apply custom function to two columns in my table. Ideally, I would r

Answer 1

In many cases it's sufficient to create a vectorized version of the function:

your_function_V <- Vectorize(your_function)

The vectorized function is then usable in a dplyr's mutate. See also this blog post.

The function posted in the question however takes one two-dimensional input from two different columns. Therefore we need to modify this, so the inputs are individual, before we vectorize.

binom.test.p <- function(x, y) {
  # input x and y
  x <- c(x, y)
  
  if (is.na(x[1])|is.na(x[2])|(x[1]+x[2])<10) {
    return(NA)
  } 
  else {
    return(binom.test(x, alternative="two.sided")$p.value)
  }
} 

# vectorized function
binom.test.p_V <- Vectorize(binom.test.p)

table %>%
  mutate(Ratio = binom.test.p_V(ref_SG1_E2_1_R1_Sum, alt_SG1_E2_1_R1_Sum))

# works!