Piwik\Plugins\CoreVisualizations\Visualizations\JqplotGraph\Pie::afterAllFiltersAreApplied PHP Method

    public function afterAllFiltersAreApplied()
    {
        parent::afterAllFiltersAreApplied();
        $metricColumn = reset($this->config->columns_to_display);
        if ($metricColumn == 'label') {
            $metricColumn = next($this->config->columns_to_display);
        }
        $this->config->columns_to_display = array($metricColumn ?: 'nb_visits');
    }