Extract Elements from Various Objects

A unified extractor for retrieving components from objects generated by the Qval package.

extract(object, what, ...)

# S3 method for class 'CDM'
extract(object, what, ...)

# S3 method for class 'validation'
extract(object, what, ...)

# S3 method for class 'sim.data'
extract(object, what, ...)

Arguments

object: An object of class CDM, validation, or sim.data.
what: A character string naming the component to extract.
...: Additional arguments (unused).

Value

The requested component, whose type depends on what and the class of object.

Details

This generic function and its methods allow users to extract internal elements from objects of class CDM, validation, or sim.data without directly accessing object slots. Supported components vary by class:

CDM

analysis.obj: The underlying GDINA or BM fit object.
alpha: EAP-based attribute estimates for each individual.
P.alpha.Xi: Posterior probabilities of attribute patterns.
alpha.P: Marginal mastery probability matrix.
P.alpha: Prior attribute weights from final iteration.
Deviance: Model deviance (-2 * marginal log-likelihood).
npar: Number of estimated parameters.
AIC: Akaike Information Criterion.
BIC: Bayesian Information Criterion.
call: Original function call.

validation

Q.orig: Original Q-matrix.
Q.sug: Suggested Q-matrix.
time.cost: time cost for validation.
process: Iteration-by-item modification log.
iter: Total iterations performed.
priority: Attribute priority matrix (PAA method only).
Hull.fit: Data for Hull plot (Hull method only).
call: Original function call.

sim.data

dat: Simulated response matrix (N × I).
Q: Simulated Q-matrix.
attribute: True attribute pattern matrix (N × K).
catprob.parm: Category success probabilities list.
delta.parm: Delta parameter list.
higher.order.parm: Higher-order parameter list.
mvnorm.parm: Multivariate normal distribution parameters.
LCprob.parm: Item/category success probabilities matrix.
call: Original function call.

Methods (by class)

extract(CDM): Extract fields from a CDM object
extract(validation): Extract fields from a validation object
extract(sim.data): Extract fields from a sim.data object

Examples

library(Qval)
set.seed(123)

if (FALSE) { # \dontrun{
################################################################
# Example 1: sim.data extraction                               #
################################################################
Q <- sim.Q(3, 10)
data.obj <- sim.data(Q, N = 200)
extract(data.obj, "dat")


################################################################
# Example 2: CDM extraction                                    #
################################################################
CDM.obj <- CDM(data.obj$dat, Q)
extract(CDM.obj, "alpha")
extract(CDM.obj, "AIC")


################################################################
# Example 3: validation extraction                             #
################################################################
validation.obj <- validation(data.obj$dat, Q, CDM.obj)
extract(validation.obj, "Q.sug")
} # }