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rvariablesscopelocal

How to define 'local' variables in R?

For example, inside a for loop, I want to define some variables to do some operation, but I want them to be automatically removed once the iteration is over.

However, if I assing a value to a variable using <-, even after the execution of the loop ends, the variable still persists and I have to remove it, manually, which is quite annoying.

Solution

  • This answers illustrates the use of local within a loop in R:

    number <- 1:5
res <- numeric(5)
local(for(i in number){
  res2 <-res[i] + 42
  print(res2)
})

[1] 42
[1] 42
[1] 42
[1] 42
[1] 42

    The above does not create res2 in .GlobalEnv unlike the following:

     for(i in number){
  res2 <-res[i] + 42
  print(res2)
 }

    Alternatively, you could avoid loops and use *apply and/or use functions that use local variables by design. See examples here