计算data.frame dplyr中的连接数

Question

我有一个data.frame:

 df <- data.frame(id = rep(1:4, each = 3),x = c("A","B","C","D","E","A","A","C","D","A","C","E"))

我想计算每个id内的连接:这是我想得到的输出:

connections    |num. of connections
   A - B       | 1
   B - C       | 1
   C - D       | 1
   A - C       | 3
   A - E       | 2
   A - D       | 2
   D - E       | 1
   C - E       | 1

怎么在dplyr中做到这一点？

Answer 1

听起来你只是在找crossprod功能,你可以像这样使用:

crossprod(table(df))
#    x
# x   A B C D E
#   A 4 1 3 2 2
#   B 1 1 1 0 0
#   C 3 1 3 1 1
#   D 2 0 1 2 1
#   E 2 0 1 1 2

这将使您更接近您想要的输出:

library(reshape2)
X <- crossprod(table(df))
X[upper.tri(X, diag = TRUE)] <- NA
melt(X, na.rm = TRUE)
#    x x value
# 2  B A     1
# 3  C A     3
# 4  D A     2
# 5  E A     2
# 8  C B     1
# 9  D B     0
# 10 E B     0
# 14 D C     1
# 15 E C     1
# 20 E D     1