计算行中的元素并映射到r中的列

df <- structure(list(id = c(1L, 1L, 1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L), 
class = structure(c(1L, 2L, 1L, 1L, 2L, 3L, 1L, 2L, 2L, 4L
), .Label = c("A", "B", "C", "D"), class = "factor")), .Names = c("id", 
"class"), class = "data.frame", row.names = c(NA, -10L))

with(df, table(id, class))
#   class
#id  A B C D
#  1 3 2 1 0
#  2 1 2 0 1

xtabs(~ id + class, df)
#   class
#id  A B C D
#  1 3 2 1 0
#  2 1 2 0 1

tapply(rep(1, nrow(df)), df, length, default = 0)
#   class
#id  A B C D
#  1 3 2 1 0
#  2 1 2 0 1

这似乎是一个非常奇怪的要求,但如果你坚持使用 apply 然后是函数 count id 等于 x class 等于 y 身份证件 和 得到 a 使用嵌套 应用

uid <- unique(DF$id)
uclass <- unique(DF$class)

count <- function(x, y, DF) sum(x == DF$id & y == DF$class)
a <- apply(matrix(uclass), 1, function(u) apply(matrix(uid), 1, count, u, DF))
dimnames(a) <- list(uid, uclass)

> a
  A B c D
1 3 2 1 0
2 1 2 0 1

注意

我们用这个 DF

Lines <- "id   class
1     A
1     B
1     A
1     A
1     B
1     c
2     A
2     B
2     B
2     D"
DF <- read.table(text = Lines, header = TRUE)