I have a rather simple problem for which I would appreciate some help since I'm new to R. I 'm working with a dataset which includes amongst other things certain experimental studies on a topic and the countries in which these experiments were conducted. I want to create a contingency table with the absolute frequencies of the countries to visualize the countries in which this issue has been studied the most. The problem however is that in some cases a certain study spreads in two or three countries and I am not sure how I should include this in the dataset to be loaded in my code.
Any help on how I should organize my data and my code would be very appreciated. Thank you!