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

[Dimitri Liakhovitski]

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?


-- 
Dimitri Liakhovitski