Coloring Polygons Based on a Column
If you’d looking to quickly style your map without resorting to CartoDB or D3, you could definitely do worse than QGIS.
Step One: Open Up Your Data
Add your layer(s) using Layer > Add Layer > Add Vector Layer (or however you’d like to do it). I’m styling a shapefile of New York City school districts based on after-school program enrollment.
Step Two: Check Your Fields
Right-click your field, then select “Open Attribute Table” to see what columns you have to work with.
I think ENROLLMENT would be a good one to work with.
Step Three: Get to the Style tab
Right-click your layer again and select Properties.
Now from the left-hand tab selector, pick Style.
Step Four: Set some styles
In the upper left-hand corner where it currently says Single Symbol, change the dropdown to read Graduated. This means we’re going to change the color gradually based on a column.
- Select
ENROLLMENTfor the column to base the color on. - Change Mode to
Quantile - Change Classes to 7
- Click Classify. A few rules will appear in the area below.
- Play around with Mode and Classes to see how the boundaries change between colors.
- When you’re satisfied, click “OK”
To learn more about modes, check out Graduated Color Modes.
Step Five: Bask in glory
Looking good! Feel free to hop back into the Styles tab to change the mode, or even manually set the color bands.
Step Six: Next steps
Maybe you’d like to learn about Graduated Color Modes or how to export an image from QGIS.