Replace double/nested for loop over function that returns dataframe with apply in R

Question

Consider a function that takes in two input arguments and returns a dataframe:

myFun <- function(a, b){
   data.frame(aSQ = a^2, bSQ = b^2, SQPROD = a^2*b^2)
}

myFun(1, 1)

A double loop can be constructed over each of the arguments of this function:

results <- as.data.frame(matrix(0, nrow = 9, ncol = 3, 
                         dimnames = list(c(), c('aSQ', 'bSQ', 'SQPROD'))))
for (a in 1:3)
   for (b in 1:3)
      results[(a-1)*3+b, ] <- myFun(a, b)

How to replace this double loop with an apply construct?

Aditya · Accepted Answer · 2015-08-13T07:45:15.637

1

resList <- mapply(
   myFun,
   a = rep(1:3, times = 3), 
   b = rep(1:3, each  = 3), 
   SIMPLIFY = FALSE
)

dplyr::bind_rows(resList)

edited Aug 13 '15 at 07:45

answered Aug 13 '15 at 07:36

Aditya

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https://meta.stackexchange.com/questions/17463/can-i-answer-my-own-questions-even-if-i-knew-the-answer-before-asking – Aditya Aug 18 '15 at 07:48
May I not agree with this kind of behavior, even though? – Aug 18 '15 at 09:09
Well, I think self-answering is fine but opinions differ. Anyway, I see no evil intentions, here. – Philipp Claßen Aug 18 '15 at 22:06

Replace double/nested for loop over function that returns dataframe with apply in R

1 Answers1