dplyr count number of one specific value of variable
Try the following instead:
library(dplyr)dat %>% group_by(id) %>% summarise(cip.completed= sum(code == "a"))Source: local data frame [3 x 2] id cip.completed (dbl) (int)1 1 12 2 23 3 0This works because the logical condition code == a is just a series of zeros and ones, and the sum of this series is the number of occurences.
Note that you would not necessarily use dplyr::count inside summarise anyway, as it is a wrapper for summarise calling either n() or sum() itself. See ?dplyr::count. If you really want to use count, I guess you could do that by first filtering the dataset to only retain all rows in which code==a, and using count would then give you all strictly positive (i.e. non-zero) counts. For instance,
dat %>% filter(code==a) %>% count(id)Source: local data frame [2 x 2] id n (dbl) (int)1 1 12 2 2