Domo Phoenix Aggregations

 Hello, I'm new to Phoenix and reading the documentation I'm not able to find how can I aggreate a value.

Let's say for example, I have an input form that generates an API Dataset which I can create charts with.

An example of a simple bar chart looks like this:

In this example, I'm using postBody to make a COUNT aggregation to graph the data.

How is that possible in the Phoenix environment?

This is my code so far:

var columns = [
  {
    type: DomoPhoenix.DATA_TYPE.STRING,
    name: 'userName',
    mapping: DomoPhoenix.MAPPING.ITEM
  },
  {
    type: DomoPhoenix.DATA_TYPE.DOUBLE,
    name: 'user',
    mapping: DomoPhoenix.MAPPING.VALUE
  },
  {
      type: DomoPhoenix.DATA_TYPE.LONG,
      name: 'userName',
      mapping: DomoPhoenix.MAPPING.SERIES
  }
];

And this is my output:

Now what's being displayed with Phoenix is the sum of userId, but I want a way to display the count of a column.

I'd also like to know if there are ways to do other aggregations like sum or average, but most importantly, the COUNT of a STRING field

Thanks in advance.