Troubles using fnUpdate after filtering with fnFilter

imac

fnUpdate doesn't work in a proper way after a filtering.

After using a filter, like this for example:
[code]
tablePlugin.fnFilter('yes', 19);
[/code]

Once the table is updated showing the filtered results, I try to do an fnUpdate like this for example:
[code]
tablePlugin.fnUpdate('', 4, 3);
[/code]

And instead of updating the column number 3 for the row number 4 OF THE FILTERING RESULTS, what it does is updating the row number 4 of the NON FILTERED TABLE.

Is there any way to avoid this undesirable behavior?
I am currently getting the current row and column with my own function which returns me the selected row of the current table. Is there a way to get the real row of the non filtered table with any datatables function?

I have tried the function fnGetPositions but I don't get it working. Javascript console show this error:
[quote]Uncaught TypeError: Cannot call method 'toUpperCase' of undefined [/quote]

The line is the following:
[code]
console.log(tablePlugin.fnGetPosition($(this).parents('td')));
[/code]

Thanks.