Piwik\Plugins\VisitFrequency\Controller::getEvolutionGraph PHP Method

    public function getEvolutionGraph()
    {
        $columns = Common::getRequestVar('columns', false);
        if (false !== $columns) {
            $columns = Piwik::getArrayFromApiParameter($columns);
        }
        $documentation = $this->translator->translate('VisitFrequency_ReturningVisitsDocumentation') . '<br />' . $this->translator->translate('General_BrokenDownReportDocumentation') . '<br />' . $this->translator->translate('VisitFrequency_ReturningVisitDocumentation');
        // Note: if you edit this array, maybe edit the code below as well
        $selectableColumns = array('nb_visits_returning', 'nb_actions_returning', 'nb_actions_per_visit_returning', 'bounce_rate_returning', 'avg_time_on_site_returning', 'nb_visits', 'nb_actions', 'nb_actions_per_visit', 'bounce_rate', 'avg_time_on_site');
        $period = Common::getRequestVar('period', false);
        if ($period == 'day') {
            // add number of unique (returning) visitors for period=day
            $selectableColumns = array_merge(array($selectableColumns[0]), array('nb_uniq_visitors_returning'), array_slice($selectableColumns, 1, -4), array('nb_uniq_visitors'), array_slice($selectableColumns, -4));
        }
        $view = $this->getLastUnitGraphAcrossPlugins($this->pluginName, __FUNCTION__, $columns, $selectableColumns, $documentation);
        if (empty($view->config->columns_to_display)) {
            $view->config->columns_to_display = array('nb_visits_returning');
        }
        return $this->renderView($view);
    }