Lets Talk: Parameters

Parameters are just about as close as Tableau gets to providing out-of-the-box programming functionality.

Unlike many of the other functions in Tableau, only parameters have the ability to both hold a value, and make that value available for direct use, and what's more, is that only parameters are global, they are completely accessible by any data source, which means that you can easily control one data source from another without defining a relationship such as when blending sources, or, by renaming fields in order to allow for cross-source filtering.

Since my Tableau journey began many years ago, being the data analyst and engineer that I am, parameters were my go-to function, yet sadly, they appear to be the unsung hero of the interactive visualisation, often with users failing to realise their true power, hence this article:

It's no secret, sure I can put some great dashboards together just like the rest of you, though for me, I've always been a fan of giving my users as much data as they can handle, and letting them define their own stories, but sadly, many users begin to use Tableau from entirely the wrong angle.

I've said it before: you may well have the most awesome dashboard ever seen, but if it takes 45 seconds to render, this is 41 seconds in which your audience has checked their watch, and moved off; it is too slow.

Performance is the key, users would much rather look at a terrible dashboard that turns around in 3 seconds, than spend more than 10 seconds waiting for awesomeness to load; and then, put off by how long it took to load, users will avoid interaction as much as possible therefore, some of the best chances to identify the greatest stories will have been lost.
Can you imagine a world without Romeo & Juliette - I can, being English I had to study this to death, but still, had Shakespeare failed to tell the story, we would probably now have 'Gordon and that bit of stuff he met in the pub last Friday night'.

Parameters, allow you to really control most aspects of your visualisation from a very simple object, here I wanted to discuss some of the ways they can be used and, since v2019.2 my absolute most favouritest (I know, I made that up) function: the Change Parameter action.

Viewpoint: Parameters

The most easiest function to define, yet being a Tableau function, they have such a tiny data footprint it is almost laughable

In case you haven't read some of my other articles, lets just be clear on what Tableau is, is not, and what it is really doing:

Anything else?

Parameters are great for performance, and being a Tableau object, they are not necessarily populated direct from the data unlike quickfilters; historically, this was always a problem as in order to keep the parameter values updated, a developer would need to manually update the list every so often, which meant they were often pushed back somewhat, as they weren't as dynamic.
And then there's the fact that they are still single-select when using a list, unlike the multi-select functionality of quickfilters

Sadly, these were part of the reason why their power is often overlooked, especially following the v2019.2 game-changing functionality Tableau (Software) added to Tableau which has meant that at the very least, sole reliance on the very poor performing quickfilters can now be largely avoided.

 The game-changing update I made reference to earlier: Change Parameter action. For the v2019.2 release, Tableau (Software) introduced a new type of action that once configured:

You are now able to populate a parameter from a chart or table selection, to use wherever and however you wish; which is exactly how the two charts in the expansive section above work; and with the parameter able to recognise multiple selections by automatically inserting an ' or ' between each selected item, then the parameter does become multi-select, though you do need to be wary of how to materialise these outputs to your use.