Doing diagnostics on your model assumptions in R programming is easy. This video is about linear regression, specifically multiple regression and making sure that the assumptions of your model are met.
Just a note to those using the native pipe. In lm() it will not work using data = . . There are several solution a) data = data b) pick(x_var), or c) switch to %>%. I like the pick(x_var) option. There is a fourth option just put the model name into predict().