This is some R code for both creating the function for variance inflation factors (VIFs) as well as a quick example tacked on at the end of the script.

Essentially, the function takes an object of class "lm" or linear model and computes the Rsquared for subsequent cross-covariate regressions - once for each covariate on all other covariates.

Take note: if you have only two covariates, then the two resulting VIFs will be identical. Hence, this will only be useful to you if you suspect multicollinearity and have k>2 regressors.

The reciprocal of 1-Rsquared is the VIF, computed once for each cross-covariate regression.

A rule-of-thumb is to watch for any VIF>10 to call out that covariate as bringing about your multicollinearity.

As of now, there are no visualizations for the VIFs, that will come in a subsequent update given enough time.