|influence||Residuals and influence for regression|
|lm.obj||object of class lm or which inherits from lm.|
plot.t and plot.d take as argument the output of influence, which is a dataframe with named columns.
The studentized residuals z are approximately standard normal residuals, while the externally studentized residuals t are score test statistics for testing each point an outlier. Any point whose externally studentized residuals extends beyond the confidence bands is formally judged to be an outlier at the 5% level.
Cook's distance measures the overall influence of each observation on the regression coefficients, including the intercept. The dfbetas measure the influence of each observation on each of the individuals regression coefficients, excluding the intercept. Specifically the dfbetas are the number of standard errors by which the coefficient changes when that observation is added to the regression. Cook's distance is roughly the average of the squares of the dfbetas.
The results for generalized linear models and generalized additive models are approximate.
Gordon Smyth. Copyright © 1996-2016. Last modified: 10 February 2004