CODEWITHSUNDEEP
tcl
Oliver Scholl
Oliver Scholl

Reputation: 63

How to sort a matrix by more than one column at once

I use the package struct::matrix and want to sort a matrix by two or more columns at once. Is it possible?

I read the man page of struct::matrix but I didn't get a hint.

Upvotes: 0

Views: 104

Answers (1)

Donal Fellows
Donal Fellows

Reputation: 137587

The simplest method (because the underlying sort method is not guaranteed to be stable) is to compute an extra column that contains a compound collation key that combines the two values, then sort on that column, and finally delete the column afterwards.

$m add column [lmap primary [$m get column 1] secondary [$m get column 2] {
    # There are many ways to make collation keys; here's one suitable for simple words...
    string cat $primary "," $secondary
}]
# Sort the rows by the final (new!) column
$m sort rows end
# Delete the no-longer-needed column
$m delete column end

Upvotes: 1

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