将R中矩阵中的二维数组的行 reshape 为列

Question

考虑以下矩阵:

M <- cbind(c("ID001", "ID003", "ID002", "ID002", "ID003"),
           c("BK101", "BK145", "BK101", "BK125", "BK101"), 
           c(6, 3, 2, 7, 3))

我想 reshape 矩阵，所以我得到以下矩阵:

       BK101 BK125 BK145
ID001    6     0     0
ID002    2     7     0
ID003    3     0     3

我尝试过:

reshape(M, idvar=[,1], timevar=[,2])

但这不起作用。

Answer 1

如果您为列命名并将它们放入数据框中:

M <- data.frame("a"=c("ID001","ID003","ID002","ID002","ID003"),
                "b"=c("BK101","BK145","BK101","BK125","BK101"),
                "c"=c(6,3,2,7,3))
xtabs(c~a+b,data=M)

       b
a       BK101 BK125 BK145
  ID001     6     0     0
  ID002     2     7     0
  ID003     3     0     3