Cross-tabulation
crosstab
uses grp2idx
to
assign a positive integer to each distinct value. tbl(i,j)
is
a count of indices where grp2idx(x1)
is i
and grp2idx(x2)
is j
.
The numerical order of grp2idx(x1)
and grp2idx(x2)
order
rows and columns of tbl
, respectively.
In this case, the returned value of tbl(i,j,...,n)
is
a count of indices where grp2idx(x1)
is i
, grp2idx(x2)
is j
, grp2idx(x3)
is k
,
and so on.