I’ve been making a lot of flow maps (or origin-destination maps) this week. In making these maps, I’ve ended up with some interesting results.
This was supposed to be a flow map in Tableau to show migration between counties, but I screwed up in how I defined the paths and ended up with what I call the ‘scribble fill’
I think it is cool looking, I’m going to assume that someone will come up with a good reason to use it, and, therefore, I’m going to write up some thoughts on how to make one of these of your own! Let’s get rolling and unleash our inner toddler!
Check out the Tableau public workbook with examples…
Scribblin’ with Tableau generated lat/lon values!
I made my first scribble map with county-level geocoding data. This is super easy, but also makes it so that there is an uneven scribbly-ness to each state. States with fewer counties have fewer scribble lines. If you want to use this easy, all-Tableau method, all you need is to start with a list of counties and states.
Drop the counties and states on the viz to make a map
Change to a line mark type
Now you have some scribbles to work with. In the next section I’ll go into more detail about customizing the scribble colors and using them for data viz. It should all work the same for the Tableau generated lat/lon scribbles (but I figured I’d just write the customize your mapping details once and I wrote the second part of this post first….)
Roll your own scribble map – with whatever density of points you want!
In case you aren’t working with Tableau generated latitude and longitude values, here is an easy-ish way to get your own quick scribble data. In QGIS (a free GIS program), open up a shapefile with the geography you want to work with.
I’m using the Census 1:20million US States for this example (in case you wondered, yes, I think this is in an ugly map projection – just NAD83 coordinates (EPSG 4269), but it makes for a nice rectangle and I know that by using it, the coordinates from my next step will be in lat/lon):
I used the Vector -> Research Tools -> Random points in extent tool to generate 25,000 random points – the US data really is under there somewhere:
I then used a spatial join to cut back to just the points inside the US (since that is the only area I want to scribble) and attached the state attributes to each point, for easier scribble mapping in Tableau.
I did a bit of housekeeping and dropped the attributes that I didn’t want and added in a latitude and longitude column
I saved a CSV of the point dataset with the US state names attached to them and dropped them in Tableau.
In Tableau, join in whatever attributes you want to map with your scribble
Add latitude and longitude to your map
Disaggregate with your ID field from QGIS (you didn’t accidentally delete that, did you? Sigh…not that I’d ever make that mistake or anything…okay, I do it all the time)
Change the mark type to ‘Line’ and enjoy the gigantic scribble
Split your scribble into states by dropping the state name onto detail, or, better yet, onto color so that you can see the states in different colors. Boom.
Adjust the line size as needed.
Change to your favorite crayon color set (I followed these instructions for creating custom palettes). My map is rockin’ the Crayola ‘Color n’ Smell’ colors – issued between 1994 and 1995. The names alone are worth this color scheme (though I find ‘wash the dog’ a bit questionable).
Maybe even drop some actual data on (that dataset that you might have joined to your state points) and use that for color encoding. I had some state-level obesity rate data lying around, so joined that in using the FIPS codes for my states:
If you don’t give Tableau a path field to use in connecting the dots, the default seems to be to use longitude, so you end up with nice up-and-down scribble strokes. If you prefer side-to-side scribble strokes drop latitude on path.
If you want it to be all crazy scribble, use some other field! I’m using ID here
Now go make some fun maps, drop them on Tableau Public or post pretty pictures on Twitter and share them with me (@mapsOverlord). I want 2018 to be the year of the toddler scribble map!