orglm.fit is used to fit generalized linear models with
restrictions on the parameters, specified by giving a description of the linear predictor, a description of the error
distribution, and a description of a matrix with linear
constraints. The quadprog package is used to apply linear
constraints on the parameter vector.
orglm.fit(x, y, weights = rep(1, nobs),
start = NULL, etastart = NULL, mustart = NULL,
offset = rep(0, nobs), family = gaussian(),
control = list(), intercept = TRUE, constr, rhs, nec)x is a design matrix of dimension
n * p, and y is a vector of observations of length
n.
a description of the error distribution and link
function to be used in the model. This can be a character string
naming a family function, a family function or the result of a call
to a family function. (See family for details of
family functions.)
an optional vector of ‘prior weights’ to be used
in the fitting process. Should be NULL or a numeric vector.
starting values for the parameters in the linear predictor.
starting values for the linear predictor.
starting values for the vector of means.
this can be used to specify an a priori known
component to be included in the linear predictor during fitting.
This should be NULL or a numeric vector of length equal to
the number of cases. One or more offset terms can be
included in the formula instead or as well, and if more than one is
specified their sum is used. See model.offset.
a list of parameters for controlling the fitting
process. For orglm.fit this is passed to
glm.control.
logical. Should an intercept be included in the null model?
a matrix with linear constraints. The columns of this matrix should correspond to the columns of the design matrix.
right hand side of the linear constraint
formulation. A numeric vector with a length corresponding to the
rows of constr.
Number of equality constrints. The first nec
constraints defined in constr are treated as equality
constraints; the remaining ones are inequality constraints.
An object of class "glm" is a list containing at least the
following components:
a named vector of coefficients
the working residuals, that is the residuals
in the final iteration of the IWLS fit. Since cases with zero
weights are omitted, their working residuals are NA.
the fitted mean values, obtained by transforming the linear predictors by the inverse of the link function.
the numeric rank of the fitted linear model.
the family object used.
the linear fit on link scale.
up to a constant, minus twice the maximized log-likelihood. Where sensible, the constant is chosen so that a saturated model has deviance zero.
The deviance for the null model, comparable with
deviance. The null model will include the offset, and an
intercept if there is one in the model. Note that this will be
incorrect if the link function depends on the data other than
through the fitted mean: specify a zero offset to force a correct
calculation.
the number of iterations of IWLS used.
the working weights, that is the weights in the final iteration of the IWLS fit.
the weights initially supplied, a vector of
1s if none were.
the residual degrees of freedom of the unconstrained model.
the residual degrees of freedom for the null model.
if requested (the default) the y vector
used. (It is a vector even for a binomial model.)
logical. Was the IWLS algorithm judged to have converged?
logical. Is the fitted value on the boundary of the attainable values?
Non-NULL weights can be used to indicate that different
observations have different dispersions (with the values in
weights being inversely proportional to the dispersions); or
equivalently, when the elements of weights are positive
integers \(w_i\), that each response \(y_i\) is the mean of
\(w_i\) unit-weight observations. For a binomial GLM prior weights
are used to give the number of trials when the response is the
proportion of successes: they would rarely be used for a Poisson GLM.
If more than one of etastart, start and mustart
is specified, the first in the list will be used. It is often
advisable to supply starting values for a quasi family,
and also for families with unusual links such as gaussian("log").
For the background to warning messages about ‘fitted probabilities numerically 0 or 1 occurred’ for binomial GLMs, see Venables & Ripley (2002, pp. 197--8).
Dobson, A. J. (1990) An Introduction to Generalized Linear Models. London: Chapman and Hall.
Hastie, T. J. and Pregibon, D. (1992) Generalized linear models. Chapter 6 of Statistical Models in S eds J. M. Chambers and T. J. Hastie, Wadsworth & Brooks/Cole.
McCullagh P. and Nelder, J. A. (1989) Generalized Linear Models. London: Chapman and Hall.
Venables, W. N. and Ripley, B. D. (2002) Modern Applied Statistics with S. New York: Springer.