I have a data frame. I'm trying to create a dummy variable that is the maximum of 3 columns for a given row.
for(i in 1:nrow(data))
{
data[i,]$max_metric <- max(data[i,]$a,
data[i,]$b,
data[i,]$c)
}
This code works, but it's definitely not the best way to do it. Are there any other ways to do this?
Use pmax, which takes the element-wise maximum of all arguments passed to it. However, this means you can't just pass the whole data.frame.
# this won't work because data[,c("a","b","c")] is one argument
data$max_metric <- pmax(data[,c("a","b","c")])
But you can pass each column of the data.frame to pmax via do.call because the second argument to do.call should be a list and data.frames are lists (with some attributes).
data$max_metric <- do.call(pmax, data[,c("a","b","c")])
# if you want na.rm=TRUE
data$max_metric <- do.call(pmax, c(data[,c("a","b","c")],list(na.rm=TRUE)))
