[jQuery] sort table by class

[Luciano]

hi,
i want create sort table in 3 tables byclass

the code:
                $(".box table").tableSorter({
                        sortColumn: 'name',
                        sortClassAsc: 'header-asc',
                        sortClassDesc: 'header-desc',
                        highlightClass: 'highlight',
                        headerClass: 'header',
                });

but, return ERROR:
$(".caixa table").tableSorter is not a function