How to modify the coding rate with MKRWAN.h

Hello,
I started using the mkr1310 for a school project. I have to make a report on the different parameters of Lorawan (spreading factor, ADR …). I was able to modify the parameters set except for the coding rate. I analyzed the mkrwan library and even the AT commands of the muratta chip mounted on the mkr but I found nothing. So I wanted to know if it was possible to modify it and if so, how?
Thank you!!!