Assigning circle colours to map using QGIS?

Question

I am trying to make a map showing which zip codes are served by which hospitals. There are five hospitals and each can serve one or more zip codes. I'd like to show each zip code with a dots of different colors to represent the different hospitals serving that zip.

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I'm trying to assign colour circles to a map with zip codes. Each zip code has hospitals assigned to it and I would like the hospitals to be represented as colour circles on the assigned zip codes. So, for instance if a zip code has three hospitals I would like the hospitals to be represented by three different colour circles each.

The hospitals do not have addresses since they are assigned to zip codes in which they do not reside. So, I used the zip codes to get the Latitude and Longitudes. In most cases the hospitals have similar latitude and Longitude because they were assigned primarily by zip code.

I've tried layer properties and categorized symbol but it just assigns one color circle per zip code. Do you know what I'm doing wrong?

Answer 1

The two main problems you have here are a many-to-many relationship between your two datasets (one hospital can serve many zips, one zip can be served by many hospitals), and that you aren't actually showing the geographic location of the hospitals. Most GIS software doesn't handle M:M relationships well, and it takes some experience and understanding of relationships in general to know how to best address that issue depending on the data and what you want to do with it.

In your case, the simplest solution is probably to create a new point feature class with a hospital name attribute. You can then manually place point features in each of the zip codes for whichever hospitals serve it, and give them the appropriate name in the attribute field. Then your symbology as you have set it up should display the map the way you want it to.

A couple of things to note: Typically when you add xy data from a spreadsheet, the points are only temporary until you save them out to new file. Also, if there are other attributes you want to keep on the points from the spreadsheet, you'll have to make some adjustments because the available join methods don't handle the M:M relationship very well. I'm not sure exactly what method you're using to 'assign' the hospitals to the zip codes, and from the screenshots it's unclear if you have multiple points per zip code stacked on top of each other or just a single point because it's only returning the first matching record. If you have stacked points, my earlier comment about spreading them out just means editing that point layer and manually moving them around a bit in the zip code boundary so they can be seen individually.