library(magrittr)
library(data.table)
set.seed(1234)
d0 <-
  data.frame(name = LETTERS[1:10],
             referrer1 = sample(c(letters[1:4], NA), 10, replace = T))
print(d0)
dcast(d0, name ~ referrer1, fun = length) %>%
  subset(select = -`NA`)