When you use compose(), the functions are passed from right to left — that is to say in the same order as the one you would use in a nested call in base R: the first function to be executed is the function on the right.

In other words, if you are used to the pipe, the order is the opposite one:

``` r

With the pipe

1:28 %>% mean() %>% round()

In base R

round(mean(1:28))

With compose

roundedmean <- compose(round, mean) rounded

So, what's the correct way to write a function that will count the number of NA?