Dataframe create new column based on other columns

Question

I have a dataframe:

df <- data.frame(\'a\'=c(1,2,3,4,5), \'b\'=c(1,20,3,4,50))
df
    a    b
1   1    1
2   2   20
3   3    3
4   4    4
5   5   50
         


        

Answer 1

A solution with apply

myFunction <- function(x){
  a <- x[1]
  b <- x[2]
  #further values ignored (if there are more than 2 columns)
  value <- if(a==b) a + b else b - a
  #or more complicated stuff
  return(value)
}

df$c <- apply(df, 1, myFunction)