从伪编码观察中创建共生矩阵

Question

是否有一种简单的方法可以将数据框与虚拟对象转换为包含两个方面共同计数的共现矩阵？

例如,从这里开始

X <- data.frame(rbind(c(1,0,1,0), c(0,1,1,0), c(0,1,1,1), c(0,0,1,0)))
X
  X1 X2 X3 X4
1  1  0  1  0
2  0  1  1  0
3  0  1  1  1
4  0  0  1  0

对此

   X1 X2 X3 X4
X1  0  0  1  0
X2  0  0  2  1
X3  1  2  0  1
X4  0  1  1  0

Answer 1

这样就可以了:

X <- as.matrix(X)
out <- crossprod(X)  # Same as: t(X) %*% X
diag(out) <- 0       # (b/c you don't count co-occurrences of an aspect with itself)
out
#      [,1] [,2] [,3] [,4]
# [1,]    0    0    1    0
# [2,]    0    0    2    1
# [3,]    1    2    0    1
# [4,]    0    1    1    0

要将结果与您显示的结果完全相同,您可以执行以下操作:

nms <- paste("X", 1:4, sep="")
dimnames(out) <- list(nms, nms)
out <- as.data.frame(out)