The code bellow, illustrate the examination of a model:

fit = lm(y ~ x1 + x2, data=mydata2) # Your model

summary(fit) # The summary of the results

vcov(fit) # The covariance matrix for model parameters

Also, at the following link [1] you can find a full tutorial about Logistic Regression in R language.

[1] http://ww2.coastal.edu/kingw/statistics/R-tutorials/logistic.html

Dimitris

A slight edit to Dimitris' code, to make it a logistic regression, use:

fit = glm(y ~ x1 + x2 + xn, family='binomial', data=mydata)

As a new R user, I strongly recommend to use help commands like

> ?lm

> ?glm

?function_name give you information about the parameters and the objects that the program creates, including the covariance matrix...