Proper idiom for adding zero count rows in tidyr/dplyr

Question

Suppose I have some count data that looks like this:

library(tidyr)
library(dplyr)

X.raw <- data.frame(
    x = as.factor(c(\"A\", \"A\", \"A\", \"B\", \         


        

Answer 1

You could explicitly make all possible combinations and then joining it with the tidy summary:

x.fill <- expand.grid(x=unique(x.tidy$x), x=unique(x.tidy$y)) %>%
    left_join(x.tidy, by=("x", "y")) %>%
    mutate(count = ifelse(is.na(count), 0, count)) # replace null values with 0's