getContrasts {gnm} | R Documentation |
For each set in a specified list of sets of parameters from a
gnm
model, computes the estimated simple contrasts (i.e.,
differences) with the first parameter in the set, and estimated standard
errors for those estimated differences. Where possible, quasi standard
errors are also computed.
getContrasts(model, sets = NULL, nSets = 1, ...)
model |
a model object of class "gnm" |
sets |
a vector of indices (if nSets is 1) or
a list (of length nSets ) of such vectors; or NULL |
nSets |
the number of vectors of indices to use |
... |
arguments to pass to other functions |
The indices must all be in 1:length(coef(object))
. If
sets = NULL
, a Tk dialog is presented for the selection
of indices (model coefficients).
For each set of coefficients selected, differences with the first coefficient and their standard errors are computed. A check is performed first on the estimability of all such differences.
A list (normally of length nSets
) of objects of class qv
(see
qvcalc
).
David Firth
Firth, D (2003). Overcoming the reference category problem in the presentation of statistical models. Sociological Methodology 33, 1–18.
Firth, D and Menezes, R X de (2004). Quasi-variances. Biometrika 91, 65–80.
gnm
, se
,
checkEstimable
, qvcalc
set.seed(1) data(yaish) ## Fit the "UNIDIFF" mobility model across education levels unidiff <- gnm(Freq ~ educ*orig + educ*dest + Mult(Exp(-1 + educ), -1 + orig:dest), family = poisson, data = yaish, subset = (dest != 7)) ## Examine the education multipliers (differences on the log scale): getContrasts(unidiff, grep("Mult1.Factor1", names(coef(unidiff))))