Loop and create list using R

Question

Using R studio I would like to create a dynamic list using a loop. The loop is indexed by a and b, including another specification in the loop the structure is not anymore working and as result I get into the list only the last value. Below the code. Any suggestion?

mylist <- list()

vec_a <- c(1,2)
vec_b <- c(5,6)

for (a in vec_a) for (b in vec_b) {
  print(a)
  print(b)
  multp <- a*b
  print(multp)
  #mylist[i] <- multp
}

#solution not working
for (a in vec_a) for (b in vec_b) for (i in 1:dim(expand.grid(tau_c,HoR_c))[1]) {
  #print(a)
  #print(b)
  multp <- a*b
  #print(multp)
  mylist[i] <- multp #the list should contain the output for each iteration
}

In the first loop you have `mylist[i]` but `i` is not defined for that loop. In the second, `tau_c` and `HoR_c` are not defined. — Ronny Efronny, Dec 05 '19 at 13:04
Try using ``` multp [i] <- a*b ``` because seems you are not saving the hole list but only the last value. — programandoconro, Dec 05 '19 at 13:11

Ronny Efronny · Accepted Answer · 2019-12-05T13:36:35.450

1

I'm assuming the list should be of length length(vec_a) * length(vec_b). I would suggest simply using an iterator like:

i <- 0
for (a in vec_a) {
    for (b in vec_b) {
        i <- i + 1
        # i <- i + 0 before edit
        multp <- a * b
        mylist[i] <- multp
    }
}

edited Dec 05 '19 at 13:36

answered Dec 05 '19 at 13:10

Ronny Efronny

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Good Idea, changing i <- i+0 with i <- i+1 in the loop works well – Jordan_b Dec 05 '19 at 13:31
Lol woops I'll change it. – Ronny Efronny Dec 05 '19 at 13:36

Loop and create list using R

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