Say I have 5 items A, B, C, D, E in a questionnaire and got respondents to rank them. The data looks like this,
> df
rank1 rank2 rank3 rank4 rank5
1 A B C D E
2 A C B D E
3 C A B E D
4 B A C D E
5 A B D C E
How do I count the frequency of each rank by item so the output looks like this,
item rank1 rank2 rank3 rank4 rank5
1 A 3 2 0 0 0
2 B 1 2 2 0 0
3 C 1 1 2 1 0
4 D 0 0 1 3 1
5 E 0 0 0 1 4
We can use table after converting to factor using base R
lvls <- sort(unique(unlist(df)))
sapply(df, function(x) table(factor(x, levels =lvls)))
# rank1 rank2 rank3 rank4 rank5
#A 3 2 0 0 0
#B 1 2 2 0 0
#C 1 1 2 1 0
#D 0 0 1 3 1
#E 0 0 0 1 4
Or calling table only once
table(unlist(df), c(col(df)))
# 1 2 3 4 5
# A 3 2 0 0 0
# B 1 2 2 0 0
# C 1 1 2 1 0
# D 0 0 1 3 1
# E 0 0 0 1 4
Or compactly with mtabulate from qdapTools
library(qdapTools)
t(mtabulate(df))
df <- structure(list(rank1 = c("A", "A", "C", "B", "A"), rank2 = c("B",
"C", "A", "A", "B"), rank3 = c("C", "B", "B", "C", "D"), rank4 = c("D",
"D", "E", "D", "C"), rank5 = c("E", "E", "D", "E", "E")), .Names = c("rank1",
"rank2", "rank3", "rank4", "rank5"), class = "data.frame", row.names = c("1",
"2", "3", "4", "5"))