gpcmtree | R Documentation |
Recursive partitioning (also known as trees) based on generalized partial credit models (GPCMs) for global testing of differential item functioning (DIF).
gpcmtree(formula, data, weights = NULL,
grouppars = FALSE, vcov = TRUE, nullcats = "downcode",
start = NULL, method = "BFGS", maxit = 500L,
reltol = 1e-10, minsize = 500, ...)
## S3 method for class 'gpcmtree'
plot(x, type = c("regions", "profile"), terminal_panel = NULL,
tp_args = list(...), tnex = 2L, drop_terminal = TRUE, ...)
formula |
A symbolic description of the model to be fit. This should be of type |
data |
a data frame containing the variables in the model. |
weights |
an optional vector of weights (interpreted as case weights). |
grouppars |
logical. Should the estimated distributional group parameters of a multiple group model be included in the model parameters? |
vcov |
logical or character specifying the type of variance-covariance matrix (if any) computed for the
final models (see |
nullcats |
character string, specifying how items with null categories (i.e., categories not observed)
should be treated. See |
start |
an optional vector or list of starting values (see |
method |
control parameter for the optimizer employed by |
maxit |
control parameter for the optimizer employed by |
reltol |
control parameter for the optimizer employed by |
minsize |
integer specification of minimum number of observations in each node, which is passed to
|
... |
arguments passed to |
x |
an object of class |
type |
character specifying the type of plot. |
terminal_panel , tp_args , tnex , drop_terminal |
arguments passed to |
Generalized partial credit model (GPCM) trees are an application of model-based recursive partitioning
(implemented in mob
) to GPCM models (implemented in gpcmodel
).
Various methods are provided for "gpcmtree"
objects, most of them inherit their behavior from
"modelparty"
objects (e.g., print
, summary
). Additionally, dedicated extractor
functions or provided for the different groups of model parameters in each node of the tree:
itempar
(item parameters),
threshpar
(threshold parameters),
guesspar
(guessing parameters),
upperpar
(upper asymptote parameters).
An object of S3 class "gpcmtree"
inheriting from class "modelparty"
.
mob
, plmodel
,
rstree
, pctree
, raschtree
, npltree
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