a <- function(matrix){
c = nrow(matrix)；
n = sum(matrix);
sum_po = 0;
sum_pe = 0;
for (i in 1:c){
sum_po = sum_po + matrix[i,i];
row = sum(matrix[i,]);
col = sum(matrix[,i]);
sum_pe = sum_pe + row * col;
po = sum_po/n;
pe = sum_pe/(n*n);
}
print(po);
print(pe);
print((po - pe)/(1-pe))
};
k = matrix(c(239, 16, 6, 21, 73, 9, 16, 4, 280), nrow = 3)
a(k)