Question

I have a data.frame df like this:

df <- data.frame (x=1:5,y=1:5)

I want to use an apply function row-wise to this data frame, where I check a condition that is dependent on both the x and y and then change the x and y elements until they meet my condition. In this example if x and y don’t add up to 8 I keep picking new random numbers for them and try again.

I figured an apply function using a while loop would be best. So I tried the following:

checkchange <- function(x) while(x[1] + x[2] < 8) 
              { 
              x[1] <- sample(5,1)
              x[2] <- sample(5,1)
              return(cbind(x[1],x[2]))
      }

I would then plan on doing this:

newdf <- apply(df,1,checkchange)

This doesn’t work. Should I be using repeat and a break or do I need to specify a return value more clearly. while loop grammar help greatly appreciated.

Answer 1

You are missing the curly braces for your anonymous function

This works for me:

checkchange <- function(x) 
              { 
              while((x[1] + x[2]) < 8)
                {
                x[1] <- sample(5,1)
                x[2] <- sample(5,1)
                }
              return(cbind(x[1],x[2]))
              }