Creating Pie Chart using related data in first portal row
I may be doing this wrong but I want to create a pie chart but one of the data points I want to use is in a related table and I want to pull the data from the most recent related record to use in this chart. For example. I have a list of table called Cars with each record being specific car. I also have a related table called Travel. Everytime a car goes on a trip, a new travel record is created showing it's current location. On my car layout, I have my travel portal sorted by most recent entry/location. There are only 5 different locations that these cars can go.
So i'd like to create a pie chart (or bar chart) showing the different locations with the number of cars at each location.
Currently I'm trying to make this chart on the cars table... maybe I need to create it in the travel table.
Any advice would be appreciated.