hadley · May 31, 2016 17:47
diff --git a/dt-mutation.r b/dt-mutation.r
 library(data.table)
 dt <- data.table(x = 1:10)

 bad_fun <- function(x) {
  if (x > 5)
    stop("Uhoh")
  x * 10L
 }
 dt[, x := bad_fun(x), by = x]
 dt


 slow_fun <- function(x) {
  Sys.sleep(10)
  x * 10L
 }
 dt[, x := slow_fun(x), by = x]
 dt
	library(data.table)
	dt <- data.table(x = 1:10)

	bad_fun <- function(x) {
	if (x > 5)
	stop("Uhoh")
	x * 10L
	}
	dt[, x := bad_fun(x), by = x]
	dt


	slow_fun <- function(x) {
	Sys.sleep(10)
	x * 10L
	}
	dt[, x := slow_fun(x), by = x]
	dt