Day 3: Dual Axis Maps - Filled and Points

It was a faithful day a little less than three years.  I was asked to pick a dashboarding software and in an afternoon I downloaded Tableau, Qlik, and Spotfire.  I had to deal with a lot of geospatial data and I quickly determined that Tableau had the best native mapping capabilities of the three.  The rest, as they say, is history.  Looking back, it was probably one of the best decisions of my life - at least it's working out so far :)

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Ah mapping. It's simple, it's easy, often times a double click away.  But there are occasions when we need to take mapping to the next level.  So let's dig in.

The business problem is that the US is broken into four regions based on state, and the end user wants to look at profitability by city.  Either one of those maps is pretty quick and easy to make in Tableau.  Problem is they want to be able to look at both region by state and profitability by city at the same time.  Dual axis maps to the rescue!

To start, let's show how to make each map individually, and then we'll bring them together.  Regions by state is up first.  We'll be using the Superstore dataset again today.  On a blank sheet start by double clicking "State".  Tableau knows that this is geospatial data (as evidenced by the globe next to the word "State"), so double clicking automatically brings up a map with points.  Change the chart type to a filled map, drop "Region" on the colors shelf  (I switched to Green-Orange 6 Palette), and boom:

I'll duplicate this sheet and start charging after profitability by city.  I'll start by hitting the "+" on state to take the next step down on the location hierarchy to city.  I'll ok the warning that filled maps doesn't work with cities, and switch the chart type to circles.  I'm done with "Regions" for the moment, so I'll remove it from the colors shelf and replace it with "Profit".  To avoid the Christmas theme (it's April, remember?) I'll click on the color legend and switch to red-black diverging (red is bad and black is good!).  Lastly, I'll bring "Sale" and drop it on the size shelf.  I now have a map showing a circle each of my cities, the size of which show total sales and colored by whether or not it's profitable.  It'll look something like this:

Two maps, both helpful.  Now that we know how to create each one let's bring them together.  Hop back over to your first map (filled by region) and duplicate it again.  We'll start with this one as we'll want the cities on top of the states/regions.

And here comes the hack. Hold down Ctrl and click and drag the Latitude pill on the rows shelf to create a duplicate one next to it.  You  should now have two of the exact same maps right next to each other.  

Right click that second pill you just created and select "Dual Axis" - now it goes back to one map.  But actually it's two identical maps stacked on top of each other.   Each of those stacked maps is independent of the other when it come to what you put on the shelf.  Each of the stacked items shows up where the marks are.  We'll click on the bottom one and change what's on the shelves to be the same setup as our profitability by city was:

If you've got it all right you should now have your dual axis map showing both region by state and profitability by city at the same time!

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Boom! Hope found that helpful!  If so, let me know.  Many thanks!

Nelson