R中5个排名的频率统计

假设我有 5 件商品A, B, C, D, E并让受访者对它们进行排名。数据看起来像这样，

> 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

如何按项目计算每个排名的频率，以便输出如下所示，

  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

我们可以用table转换为后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

或致电table只有一次

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

或者紧凑地与mtabulate from qdapTools

library(qdapTools)
t(mtabulate(df))

data

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"))