Frequency cross tabulation with combinations of binary variables in R

Question

I have a data frame which looks like this:

df <- data.frame(dummyA=c(0,0,1,0,1), dummyB=c(1,1,0,1,1), dummyC=c(0,0,1,1,1))

> df
  dummyA dummyB dummyC
1      0      1      0
2      0      1      0
3      1      0      1
4      0      1      1
5      1      1      1

Are there ways to cross-tabulate frequency of all conbinations as illustrated below? I need to tabulate it in matrix format.

There are two rows with dummyA=1 (row# 3 and 5), thus left-top cell is 2. There is one row (#5) with dymmyA=1 and dmmyB=1, thus left-middle cells is 1. Two rows (#3 and 5) has dymmyA=1 and dymmyC=1, thus left-bottom cell is 2.

There are a lot of posts which deal with cross tabulation in R but I have not found this type of tabulations yet. I prefer dplyr for data manipulation but any suggestions are highly appreciated.

Answer 1

df <- data.frame(dummyA=c(0,0,1,0,1), dummyB=c(1,1,0,1,1), dummyC=c(0,0,1,1,1))

df
#>   dummyA dummyB dummyC
#> 1      0      1      0
#> 2      0      1      0
#> 3      1      0      1
#> 4      0      1      1
#> 5      1      1      1

m <- as.matrix(df)

crossprod(m, m)
#>        dummyA dummyB dummyC
#> dummyA      2      1      2
#> dummyB      1      4      2
#> dummyC      2      2      3

^{Created on 2023-11-21 with reprex v2.0.2}