The standard errors are a key element while presenting the results
of a model. They are the second column of the table of coefficient
and are used to compute the t/z-value. stderr enables to retrieve
easily the vector of standard errors, either from a fitted model or
from a matrix of covariance
stder(x, .vcov, ...)# S3 method for default
stder(x, .vcov = NULL, ...)
a numeric vector
a fitted model or a matrix of covariance
a function that computes a covariance matrix, or a character
further arguments