temp = sapply(colnames(A), function(x)
sapply(colnames(A), function(y)
sum(rowSums(A[,c(x, y)]) == 2)))
diag(temp) = 0
temp
# A B C D E F
#A 0 0 0 0 1 0
#B 0 0 2 1 1 1
#C 0 2 0 3 2 2
#D 0 1 3 0 2 1
#E 1 1 2 2 0 1
#F 0 1 2 1 1 0
library(reshape2)
library(ggplot2)
df1 = melt(temp)
graphics.off()
ggplot(df1, aes(x = Var1, y = Var2, fill = value)) +
geom_tile() +
theme_classic()

DATA
A = structure(list(A = c(0L, 0L, 1L, 0L, 0L), B = c(1L, 1L, 0L, 0L,
0L), C = c(1L, 1L, 0L, 1L, 1L), D = c(1L, 0L, 0L, 1L, 1L), E = c(1L,
0L, 1L, 1L, 0L), F = c(0L, 1L, 0L, 1L, 0L)), .Names = c("A",
"B", "C", "D", "E", "F"), class = "data.frame", row.names = c("1",
"2", "3", "4", "5"))