r lm function validating linear model r model predicts what year is a model valid in r r lm how to check model how to validate linear model in r how to test a linear model in r how is validation of model in r is r based on previous month data lm model for r how to validate a linear model in r how do you validate a linear model in r r lm predicting months what data does r use to validate a linear model? how does r validate a linear model r how to validate a model what data is used to validate model r r lm definition how to validate r model with lm how to validate linear model with r lm