r.squared(object, model = NULL, type = c("cor", "rss", "ess"), dfcor = FALSE)
"plm"
,NULL
, the transformation used to estimate the
model is also used for the computation of R squared,"rss"
(residual sum of squares),
"ess"
(explained sum of squares), or
"cor"
(coefficient of correlation between the fitted values and the
response),TRUE
, the adjusted R squared is computed.