SharePoint 2013 rest API get the average of calculated column

Question

I have a calculated column for ticket response time Want to get the average response time for all tickets

average response time = (sum of #response time)/ #of tickets

call: https://siteurl/_api/web/lists/getbytitle('listName')Items/?$select=Response_x0020_Time

function successCall(data){
  var myListData = data.d.results.length

  $('#divAction').html(myListData)
}

I am not sure how to extract the data to compute the average

Any help would be greatly appreciated!

Answer 1

First, you're missing a slash between getbytitle('listname') and Items, should be:

<siteurl>/_api/web/lists/getbytitle('<listname>')/Items/?$select=Title,Response_x0020_Time

Now I'm going to have to make some assumptions, because you didn't provide any information about the field types upon which the calculation is based, or the expected type of the calculation.

I'm going to assume that Response_x0020_Time is the calculation of an end date minus a start data. That would make the result a float (where 1 equals one day). But it won't come back as a float in the response JSON, because it's a calculated field which the REST api will just return it as a string, so we'll need to convert that to a float.

Also, because of the way you've written your success function, I assume you're using jQuery's $.ajax to perform the REST service call.

Given that, you would process the response something like:

var sum = 0;

// data.responseJSON.d.results is an array of items returned
for(var i=0; i<data.responseJSON.d.results.length; i++) {

    // get the current item
    var current = data.responseJSON.d.results[i];

    // convert it's response time to a float and add it to sum
    sum += parseFloat(current["Response_x0020_Time"]);
}

// now divide sum by the length of the array
var average = sum / data.responseJSON.d.results.length;

// shove it into the div
$('#divAction').html(average)