Changing the Code Rate in LoRaWan

Hi, 
I am new to flora. I want to change the code rate and see the performance. The default value value is set to for LoRaCR is 4 which means code rate is 4/8. If I want to change it to 4/5, 4/6, 4/7, what values should I assign in the SimpleLoraApp.ned ?

