Parameters VS Filters

I've been using Parameters a lot these days. The use is so broad I just can't stay away from it. Tableau made filter super easy to use, but sometimes in addition to filters I might want to display the graph differently, this is when parameters come in super handy. It was quite intimidating the first few times I've had to use parameters, but once I got the hang of it, it became one of those tools I come back to over and over again.

This is a simple dashboard I made to illustrate the difference between parameters and filters.
Disclaimer: there are other ways of using parameters, this is just one of the most common ways I've had to use them for.

First, I got a simple demographic data set from UN Data, chose the last 3 year for Canada and cleaned it up a bit (2012 data was not part of the data set). This is how my data source looks like:

I knew I wanted to see population over time as a bar graph, so I dragged:

• Year to Columns
• SUM(Value) to Rows

I then wanted to stack the bar as well as filter the bars a few ways. So I created a parameter and 3 quick filters.

Add Filters

• Simply select the filters you'd like using quick filters

Add Parameters

• Create a parameter first. I called mine "Stack Bar Graph By" (not the best name I know), data type is String, and I used a List

• Create a calculated field that uses the parameters. I called mine "Stack Bar Filter", and here's the syntax I used:

          CASE [Stack Bar Graph By]

          WHEN '1' THEN [Age]

          WHEN '2' THEN [Marital status]

          WHEN '3' THEN [Sex]

          WHEN '4' THEN NULL

          END

• Next, drag the calculated field to Color, and Show Parameter Control

The Difference

The Age filter on the default view is limited to ages 25 - 44. If you select all the age ranges, you will see a much busier graph. The same is with the Marital Status filter. I've limited the default to just 3 statuses, this filters out all the people with the other 3 statuses that's not chosen.

Default View with All Age Groups - Parameter on Age

Note that when you select all the ages, additional colours appeared in the graph (above), but when you select all the marital statuses, the individual portions of the existing colors simply increased in size. This is because the default parameter is on Age.

If you change the parameter to Marital Status, and then select all the marital statuses, you will now see additional colors in the bar graph.

All Marital Statuses - Parameter on Marital Status

Depending on the purpose of the graph/dashboard, filters and parameters provide their own purpose and can compliment each other. In this case, the filters let you look at a specific subset of the entire population by Age, Marital Status, and Sex, whereas the parameters let you see the proportions between each of the subsets in relation to one another.

Other examples of uses for parameters I've used in the past include:

• Switching between a bar graph and a line graph
• Change the time unit the graph is laid out (day/week/month/year)
• Switching between a few different unit of measurements (ie. meter vs inch)
• Basically, switch any of the pills in any of the shelves (ex. rows, columns, colours...etc.)

References: Tableau Parameter Help