[R] dplyr - counting a number of specific values in each column - for all columns at once

[Hadley Wickham]

On Tue, Jun 16, 2015 at 12:24 PM, Dimitri Liakhovitski
<dimitri.liakhovitski at gmail.com> wrote:
> Hello!
>
> I have a data frame:
>
> md <- data.frame(a = c(3,5,4,5,3,5), b = c(5,5,5,4,4,1), c = c(1,3,4,3,5,5),
>       device = c(1,1,2,2,3,3))
> myvars = c("a", "b", "c")
> md[2,3] <- NA
> md[4,1] <- NA
> md
>
> I want to count number of 5s in each column - by device. I can do it like this:
>
> library(dplyr)
> group_by(md, device) %>%
> summarise(counts.a = sum(a==5, na.rm = T),
>           counts.b = sum(b==5, na.rm = T),
>           counts.c = sum(c==5, na.rm = T))
>
> However, in real life I'll have tons of variables (the length of
> 'myvars' can be very large) - so that I can't specify those counts.a,
> counts.b, etc. manually - dozens of times.
>
> Does dplyr allow to run the count of 5s on all 'myvars' columns at once?

md %>%
  group_by(device) %>%
  summarise_each(funs(sum(. == 5, na.rm = TRUE)))

Hadley

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