Merge pull request hadley#79 from OaCantona/patch-4

Difference in code

iteration.Rmd

@@ -100,7 +100,7 @@ Every for loop has three components:
     it's easy to create them accidentally. If you use `1:length(x)` instead
     of `seq_along(x)`, you're likely to get a confusing error message.
     
-1.  The __body__: `output[i] <- median(df[[i]])`. This is the code that does
+1.  The __body__: `output[[i]] <- median(df[[i]])`. This is the code that does
     the work. It's run repeatedly, each time with a different value for `i`.
     The first iteration will run `output[[1]] <- median(df[[1]])`, 
     the second will run `output[[2]] <- median(df[[2]])`, and so on.