logLik.glm {base}

R Documentation

Extract Log-Likelihood from an glm Object

Description

Returns the log-likelihood value of the generalized linear model represented by object evaluated at the estimated coefficients.

Usage

## S3 method for class 'glm'
logLik(object, ...)

Arguments

object	an object inheriting from class "glm".
...	further arguments to be passed to or from methods.

Details

As a family does not have to specify how to calculate the log-likelihood, this is based on the family's function to compute the AIC. For gaussian, Gamma and inverse.gaussian families it assumed that the dispersion of the GLM is estimated and has been included in the AIC, and for all other families it is assumed that the dispersion is known.

Not that this procedure is not completely accurate for the gamma and inverse gaussian families, as the estimate of dispersion used is not the MLE.

Value

the log-likelihood of the linear model represented by object evaluated at the estimated coefficients.

See Also

glm, logLik.lm

Examples

##-- Continuing the  glm(.) example:
Eq <- function(x,y) all.equal(x,y, tol = 1e-12)
stopifnot(Eq(AIC(anorex.1), anorex.1$aic),
          Eq(AIC(g1), g1$aic),
          Eq(AIC(g2), g2$aic))
## next was wrong in 1.4.1
x <- 1:10
lmx <- logLik(lm(x ~ 1)); glmx <- logLik(glm(x ~ 1))
stopifnot(all.equal(as.vector(lmx), as.vector(glmx)),
          all.equal(attr(lmx, 'df'), attr(glmx, 'df')))

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