Subtract the index of one dataframe from a list with another data frame of a different list-CodePudding

I have two lists of data frame, with binary values in them.

As an example : The first list is lst1 and it contains the following values

$`4`
 [1] "N" "N" "N" "A" "A" "A" "A" "N" 

$`7`
 [1] "N" "N" "N" "N" "N" "N" "N" "N"

The second list is lst2 and it contains the following values

$`4`
 [1] "N" "N" "A" "A" "A" "A" "A" "N" "N" "N" 
$`7`
 [1] "N" "N" "N" "N" "N" "N" "N" "N" "N" "N"

I want to subtract the index of lst2 from lst1 at the first instance of "A".

So in lst1, at dataframe $`4` , the index value of "A" is 4. similarly in lst2 at $`4` , the index value of "A" is 3 . The difference between them would be 4-3 = 1. And so on for other data frames in the list.

I have tried looking for a couple of solutions, but I am at my wit's end. Thank you!

CodePudding user response：

I wrote a function to calculate the expected difference. It returns a list with the same names as the argument lists, with the calculated difference.

Keep in mind two important things:

The difference could not be calculated if "A" doesn't appear in any of the vectors (that's the case with vector 7).
If names do not match, the calculation doesn't have any sense, that's why I throw an error (stop)

This is the function code:

calcDif = function(lst1, lst2){
  if (!identical(names(lst1), names(lst2))){
    stop("Names do not match!")
  }

  difs = list()
  for (i in names(lst1)){
    idx1 = min(which(lst1[[i]] == "A"))
    idx2 = min(which(lst2[[i]] == "A"))
    difs[[i]] = idx1 - idx2
  }
  return(difs)
}

If I run it with your data, I get:

calcDif(lst1, lst2)
$`4`
[1] 1

$`7`
[1] NaN

Warning messages:
1: In min(which(lst1[[i]] == "A")) :
  no non-missing arguments to min; returning Inf
2: In min(which(lst2[[i]] == "A")) :
  no non-missing arguments to min; returning Inf

If I attempt to run it with lists of unmatching names, then:

calcDif(list(x = 1:2), lst2)
Error in calcDif(list(x = 1:2), lst2) : Names do not match!