R^2 of regressed line fitted through origin

Hi there! In order to help you more, we need you to make a Reproducible Example, or reprex for short. You can learn more about making one here:

In particular, to figure out why you're getting different results between R and other software, we need access to the data frame you're working with, datafm. You might also want to check out this post on prepping your data for a reprex: