Using variables names in loops

[NosajW]

Hi there,

I am kind of you to R, I used to work on Stata, so it is kind to make the change.

I wish to run through variables using their names.

a1 = c(1,2,3,4,5,6)
a2 = c(1,2,3,4,5,6)
df = data.frame(a1,a2)
for (i in 1:2) {
  variable = paste0("a", i)
  mean = mean(as.name(variable))
  print(as.name(mean))
}

This actually doesn't work, since it is not taking the variable values but the variable as a name. On top of that I wish to create numerous mean variables using the number in the loop (for instance mean1 and mean2 in the present case).
For those of you which are familiar with Stata, here is what I'm trying to do

forvalues x = 1/2 {
gen meanx' = mean(ax')
}

Thank you so much in advance!

Bests,

[JackDavison]

The below code works:

a1 = c(1,2,3,4,5,6)
a2 = c(1,2,3,4,5,6)
df = data.frame(a1,a2)
for (i in 1:2) {
  variable = paste0("a", i)
  mean = mean(eval(parse(text = variable)))
  print(mean)
}

Converting a String to a Variable Name On-The-Fly and Vice-versa in R |...

However, there are other ways to achieve similar results.

I notice you've created a dataframe; this would also do what you want:

for (i in 1:2) {
  variable = paste0("a", i)
  mean = mean(df[[variable]])
  print(mean)
}

Or you could avoid loops altogether and use {dplyr}, which will retain your dataframe structure:

dplyr::summarise(df, dplyr::across(contains("a"), ~mean(.x)))
   a1  a2
1 3.5 3.5

[NosajW]

@JackDavison

a1 = c(1,2,3,4,5,6)
a2 = c(1,2,3,4,5,6)
df = data.frame(a1,a2)
for (i in 1:2) {
  variable = paste0("a", i)
  mean = mean(eval(parse(text = variable)))
  print(mean)
}

Thank you very very much! This is exactly what I needed.