# How to compute goodness of fit for a linear model in R

I have fit a linear model using the lm function in R...

model <- lm(trans.baseline.CD4 ~ hiv\$Julian.Date)

... and I would like to assess the quality of the model's fit. Is there a function in R that will do this? Alternatively, I found a formula for goodness-of-fit involving the sum of squared residuals given the null and alternative hypotheses, but I don't know how to get these values either. Any pointers?

Thanks!

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