Use Parameters & Custom Functions To Call APIs In Power BI

I have already written a detailed blog on how to get data in Power BI using API which you can find here.

Why this Blog?

If you are familiar with calling API’s using a programming language, you probably know how to handle paging & additional dynamic inputs in the endpoints.

Similarly, in Power BI though there is no direct method to do so, we can make use of the parameters & custom function feature to overcome the problem of paging & we can also dynamically change the text (e.g. id) in the API’s endpoint.

In this blog, I’m going to explain how you can dynamically call the API based on its location.

 

What are Parameters in Power BI?

In Power BI Desktop, you can add Query Parameters to a table/query and make elements of the table dependent on those parameters. You can have one parameter, or multiple parameters for any table. Let’s take a look at how to create parameters in Power BI Desktop.

 

Steps to Create Parameters:

Step 1: Open Power BI Desktop, from Home ribbon click on “Transform data”.

Step 2: In Power Query Editor, from Home ribbon click on Manage Parameters->New Parameter

Step 3: Fill in the details in the Manage Parameters Dialog box. (Give a name & then add a dummy value for now). Click on Ok.

Manage Parameters Dialog box

What are Custom Functions in Power BI?

In Power BI, custom functions can be used to tackle the repetitive tasks. Instead of writing the same code again and again, we can create a function for the code & execute it in multiple queries which will save our time & efforts.

In our case, we are going to use Custom Functions to dynamically change the location id in an API’s endpoint, so that we don’t have to manually call the API’s for each location.

Let’s take a look at how to create custom functions.

 

Steps to create Custom functions with Parameters:

In this example we are bringing an Event api from a popular platform which requires a Location ID present in its URL to access the data.

Step 1: Create a query by calling an api for a single location. (Enter the id manually) E.g. https://play.dhis2.org/2.34.0/api/events?paging=false&orgUnit=Il7prf3KXCf. Name the query “GetEvents”

GetEvents

Step 2: Navigate the API, extract the lists, records and finally columns. By the end of which the M code will look something like this:

Step 3: As you can see, we are entering the id after “orgunit=” in the query itself. So, the next step is to enter the same code via Parameters.

For this, change the text after “orgunit=” to point towards the parameter that we had created. The URL will now become: “https://play.dhis2.org/2.34.0/api/events?paging=false&orgUnit=”&LocationID

Meanwhile, also change the “LocationID” parameter’s value to the “id” i.e. Il7prf3KXCf

The output will remain the same, but now instead of giving the values from the URL we are giving it from the new Parameter that we had created.

 

Step 4: Now that we have a table “GetEvents”. We are going to make a function out of it. To do so, right click on “GetEvents” & select “Create Function”. A “Create Function” dialog box will pop up. Give the function a name & click on OK.

Create Function

Step 5: You will see that, Power BI will automatically group the parameter & function in a single Folder. Inside the folder is the function that has just been created called “EventFunction”.

Tip: Disable the load for “GetEvents”. Transformations done in the “GetEvents” query will reflect in the output of the function.

Dynamically bring Events for multiple Locations using Custom Functions:

I have already brought a table “Location” in Power BI from an endpoint which gives me the list of all locations in my account.

I’m going to use this table as the base table to call the events. Let’s take a look at how we can do that.

 

Step 1: Create a duplicate of “Location” query & rename it to “Events”.

Power BI

Step 2: Click on the header of the column which has the id. In this case I have clicked on “id”. Then, go to “Add column” ribbon & click on “Invoke Custom Function”

Step 3: A “Invoke Custom Function” dialog box will appear. From the Function query dropdown, select our function “EventFunction”. In LocationID dropdown, confirm that column “id” is selected. Click on Ok.

Invoke Custom Function

Step 4: Remove the errors from the newly created column & then expand the table to bring in the records & columns accordingly.

Conclusion:

In this blog, we have learnt how to use parameters & custom functions to call API’s dynamically.

You may also have noticed that this platform’s API had an option to tackle paging in one simple step. But in most cases, we have to handle paging by ourselves. Parameters & custom functions can come handy in such situations.

 

Karan Nair

Team Lead – Data Analytics

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