How to use ungrouped date fields as data for Charts Views?

Question

I have a content type with the following date fields:

1. Start Date
2. Deadline Date
3. End Date

Deadline date is programmatically calculated, where as Start and End are based on user input.

There is a page with a table view for open nodes, ones without an End Date. In it, I would like to have a graphical representation of nodes alongside a graphical representation of time left from now until End Date.

I made a chart block view with serials as labels and dates as data, but the only result I got was a flat line with 0. Then tried every format combination listed under the date field without any luck. Although that, post date as a field seems to return correct results(?).

For a specific node Devel listed the following:

created (String, 10 characters ) 1451882207

field_end_date (Array, 1 element)
    und (Array, 1 element)
    $...->field_end_date['und']
        0 (Array, 4 elements)
            value (String, 19 characters ) 2016-10-27 00:00:00
            timezone (String, 11 characters ) Asia/Riyadh
            timezone_db (String, 11 characters ) Asia/Riyadh
            date_type (String, 8 characters ) datetime

Creating timestamp fields gave the same flat line. So, I am unsure about what the exact issue is. Help would be appreciated on how to reach the desired outcome or about how to debug this if it is not a feature.

I'm using Charts version 7.x-2.x-dev.

Answer 1

I found a partial workaround for this by using hook_views_pre_render.

function hook_views_pre_render(&$view) {
   if($view->name == 'stuff'){
      $results = &$view->result;
      foreach ($results as $key => $result) {
      $now = time();
      $end = strtotime($result->field_field__end_date_[0]['raw']['value']);
      $daysuntil = date("j", $end-$now);
      $result->field_field_end_date[0]['rendered']['#markup'] = $daysuntil;
     }
   }
}

The previous function is for a chart that displays node serials as x-axis labels and number of days for yaxis, which is calculated as the difference between now and a end date.

Answer 2

Within the Charts module, there is an interesting "feature request" (not "bug" ...) about Graph node input over time (support date formatting on a continuous axis).

In Comment #3 of that issue is stated: 'The trouble here is that neither Views nor Date modules provide aggregation options for date-based fields.'.

Have a look at this issue, which I believe is similar to what you're asking here. Maybe also the patch(es) included in this issue.

Disclosure: I'm a co-maintainer of this module.