Creating a new layer from a spreadsheet and an existing shapefile in QGIS

Question

I have a map of US zip codes and a spreadsheet that associates data with specific zip codes. I want to show the zip codes where the most data exists using a gradient, but I am not even sure how to get it onto the map in the first place.

Answer 1

Since I've been helping my (non-GIS user) brother with this lately:

Essentially you have to join your data table to your shapefile, but since XLS aren't readable by QGIS, you can use CSV and accomplish the same thing.

• open your XLS and remove all formatting from the sheet, if any (ie. colours or lines or anything like that)
• ensure all the column names are short and without spaces
• note the column that holds the ZIP CODE value
• save the XLS as a CSV from excel
• using QGIS, go to the menu option Layer > Add Layer > Add Delimited Text Layer
• Browse to your CSV
• ensure the option for 'No Geometry (attribute table only) is selected next to "Geometry definition"
• once the CSV has been added to the map, open the properties (right-click / properties) for the CSV and select the 'Fields' section on the left-hand side
• Ensure all the field types are being read as INT values (rather than String, so you can do your mapping correctly) Close the properties when finished checking.
• Add your ZipCodes.shp to the map
• Right-click the ZipCodes.shp layer and open the Properties
• Select Fields from the left-hand side and note which field stores the ZIP CODE value
• Access the Join option on the left-hand side
• Click the little green cross in the bottom left of the dialogue box
• ensure the Join Layer is your CSV file
• ensure the join field and target field are the ZIP CODE value fields from each of your SHP and CSV as you checked above
• click OK
• check the Fields setting on the left, and ensure the fields from the CSV have been added to the SHP

You should now be able to do your mapping...