How to add the output "NoMissingTimeSheets" instead of Null to a custom function in Tibco Spotfire

Question

I am trying to update a custom function below, to avoid outputting blank/Null values in the solution.

checkDifference = function(A,B) {
    Av=strsplit(A,', ')[[1]]
    Bv=strsplit(B,', ')[[1]]
    Cv=setdiff(Bv,Av)
    C=paste(Cv,collapse=', ')
    return (C)
}

output=mapply(FUN=checkDifference,input1,input2)

I have tried adding an If statement below and it returns all blank rows of data.

output=if mapply(FUN=checkDifference,input1,input2) isNull then "NoMissingTimeSheets"

Answer 1

The simplest way to do this would be to modify checkDifference:

checkDifference = function(A,B) {
  Av=strsplit(A,',')[[1]]
  Bv=strsplit(B,',')[[1]]
  Cv=setdiff(Bv,Av)
  C=paste(Cv,collapse=',')
  C=ifelse(C=='','NoMissingTimeSheets',C)
  return (C)
}

output=mapply(FUN=checkDifference,input1,input2)

That is adding this line within the function:

C=ifelse(C=='','NoMissingTimeSheets',C)

because the function is applied to the two inputs (input1 and input2) as vectors, element by element, using mapply. Also, the original result C is never null but can be an empty string, so it is compared to ''.