Frequency of values per column in table

Question

What is a good way to get the independent frequency counts of multiple columns using dplyr? I want to go from a table of values:

# A tibble: 7          


        

Answer 1

library(dplyr)
library(reshape2)
df %>%
  melt() %>%
  dcast(value ~ variable, fun.aggregate=length)

#   value a b c d
# 1     1 2 0 2 1
# 2     2 1 4 2 0
# 3     3 2 2 0 6
# 4     4 0 1 2 0
# 5     5 2 0 1 0

Data

df <- structure(list(a = c(1L, 1L, 2L, 3L, 3L, 5L, 5L), b = c(2L, 2L, 
2L, 2L, 3L, 3L, 4L), c = c(1L, 1L, 5L, 4L, 2L, 4L, 2L), d = c(3L, 
3L, 3L, 3L, 3L, 3L, 1L)), .Names = c("a", "b", "c", "d"), class = "data.frame", row.names = c("1", 
"2", "3", "4", "5", "6", "7"))