I recently encounter a problem whereby sortField will treat the no data column as the column with the highest value. I think this is not logic where no data should be treated as the lowest value (or 'zero'). The reported version of zoomcharts is 1.11.5. Thank you.
null values were actually sorted correctly while undefined values were not. This has been fixed for the next version.
null
undefined
Fun JavaScript fact:
undefined - 1 => NaN null - 1 => -1