upperpar | R Documentation |
A class and generic function for representing and extracting the upper asymptote parameters of a given item response model.
upperpar(object, ...)
## S3 method for class 'raschmodel'
upperpar(object, alias = TRUE, vcov = TRUE, ...)
## S3 method for class 'rsmodel'
upperpar(object, alias = TRUE, vcov = TRUE, ...)
## S3 method for class 'pcmodel'
upperpar(object, alias = TRUE, vcov = TRUE, ...)
## S3 method for class 'nplmodel'
upperpar(object, alias = TRUE, logit = FALSE, vcov = TRUE, ...)
## S3 method for class 'gpcmodel'
upperpar(object, alias = TRUE, vcov = TRUE, ...)
object |
a fitted model object whose upper asymptote parameters should be extracted. |
alias |
logical. If |
logit |
logical. If a |
vcov |
logical. If |
... |
further arguments which are currently not used. |
upperpar
is both, a class to represent upper asymptote parameters of
item response models as well as a generic function. The generic function can
be used to extract the upper asymptote parameters of a given item response
model.
For objects of class upperpar
, several methods to standard generic
functions exist: print
, coef
, vcov
. coef
and
vcov
can be used to extract the upper asymptote parameters and their
variance-covariance matrix without additional attributes.
A named vector with upper asymptote parameters of class upperpar
and
additional attributes model
(the model name), alias
(either
TRUE
or a named numeric vector with the aliased parameters not included
in the return value), logit
(indicating whether the estimates are on the
logit scale or not), and vcov
(the estimated and adjusted
variance-covariance matrix).
personpar
, itempar
,
threshpar
, discrpar
, guesspar
if(requireNamespace("mirt")) {
o <- options(digits = 3)
## load simulated data
data("Sim3PL", package = "psychotools")
## fit 2PL to data simulated under the 3PLu
twoplmod <- nplmodel(Sim3PL$resp2)
## extract the upper asymptote parameters (all fixed at 1)
up1 <- upperpar(twoplmod)
## fit 3PLu to data simulated under the 3PLu
threeplmodu <- nplmodel(Sim3PL$resp2, type = "3PLu")
## extract the upper asymptote parameters
up2 <- upperpar(threeplmodu)
## extract the standard errors
sqrt(diag(vcov(up2)))
## extract the upper asymptote parameters on the logit scale
up2_logit <- upperpar(threeplmodu, logit = TRUE)
## along with the delta transformed standard errors
sqrt(diag(vcov(up2_logit)))
options(digits = o$digits)
}
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.