xxirt_createThetaDistribution: Creates a User Defined Theta Distribution

In sirt: Supplementary Item Response Theory Models

Creates a User Defined Theta Distribution

Description

Creates a user defined theta distribution.

Usage

xxirt_createThetaDistribution(par, est, P, prior=NULL, prior_par1=NULL,
       prior_par2=NULL, lower=NULL, upper=NULL)

Arguments

par	Parameter vector with starting values
est	Vector of logicals indicating which parameters should be estimated
P	Distribution function for \bold{\theta}
prior	Prior distribution
prior_par1	First parameter of prior distribution
prior_par2	Second parameter of prior distribution
lower	Lower bounds for parameters
upper	Upper bounds for parameters

See Also

xxirt

Examples

#############################################################################
## EXAMPLE 1: Definition of theta distribution
#############################################################################

#** theta grid
Theta <- matrix( seq(-10,10,length=31), ncol=1 )

#** theta distribution
P_Theta1 <- function( par, Theta, G){
    mu <- par[1]
    sigma <- max( par[2], .01 )
    TP <- nrow(Theta)
    pi_Theta <- matrix( 0, nrow=TP, ncol=G)
    pi1 <- stats::dnorm( Theta[,1], mean=mu, sd=sigma )
    pi1 <- pi1 / sum(pi1)
    pi_Theta[,1] <- pi1
    return(pi_Theta)
                }
#** create distribution class
par_Theta <- c( "mu"=0, "sigma"=1 )
customTheta  <- sirt::xxirt_createThetaDistribution( par=par_Theta,
                       est=c(FALSE,TRUE), P=P_Theta1 )

sirt documentation built on May 29, 2024, 8:43 a.m.