CODEWITHSUNDEEP
rdata.table
tomhiggens
tomhiggens

Reputation: 1

Within an R data.table can you add multiple columns using conditional statements?

I would like to add multiple columns to a data.table depending on the values in other columns, in one function, e.g. 

d.f <- data.frame(a=c(1,2,3),b=c(4,5,1))
d.t <- data.table (d.f)

g <- function(x,y){
  if (y>x)
     return (list(1,2))
   else 
return (list(2,1))
}
 d.t[,c('x','y'):=g(a,b)]

But this errors out, and using ifelse doesn't seem to work either.

Upvotes: 0

Views: 575

Answers (1)

shadow
shadow

Reputation: 22333

You should use ifelse instead of if (...) else. Also the return statement should be a list of length 2, with each list element having the same length as x and y. 

g <- function(x,y){
  list(ifelse(y>x, 1, 2), 
       ifelse(y>x, 2, 1))
}

Upvotes: 4

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