"Fast" binary category column generation using only R code. Response to http://rstatistics.net/strategies-to-speed-up-r-code/

fastRcategories.R

col1 <- runif (12^6, 0, 2)
col2 <- rnorm (12^6, 0, 2)
col3 <- rpois (12^6, 3)
col4 <- rchisq (12^6, 2)
df <- data.frame (col1, col2, col3, col4)

## process the rows

## slightly less than  3 times slower than Rcpp example here http://rstatistics.net/strategies-to-speed-up-r-code/  (on my machine)
## but written only in R

system.time({
want = which(rowSums(df) > 4)
output = rep("less than 4", times = nrow(df))
output[want] = "greater than 4"
})