I'm conducting an analysis from Jan to Dec where my test/treatment group is the combination of 5 stores with sales per month. The main objective is to find a control group of 10 stores over 150 available whose mean per month follows closely to the test/treatment group mean per month. I did some search and I might need to use the 'Matching' package from R with the Genetic Algorithm (GenMatch) function but I'm struggling - don't know how to configure the distance measure as the 'mean per month'.
Is this an efficient method? Any other good algorithm/method/approach to test?