R/tam_accelerate_parameters.R

In TAM: Test Analysis Modules

## File Name: tam_accelerate_parameters.R
## File Version: 9.192

##############################################################################
# acceleration
tam_accelerate_parameters <- function( xsi_acceleration, xsi, iter, itermin=2, ind=NULL)
{
    eps <- 1E-70
    parm_history <- xsi_acceleration$parm_history
    if ( is.null(ind) ){
        ind <- seq( 1, nrow(parm_history) )
    }

    #*********************************************************
    # overrelaxation method according to Yu (2012)
    if ( xsi_acceleration$acceleration=="Yu"){
        w_accel <- xsi_acceleration$w
        if ( w_accel < 0 ){
            w_accel <- .01
        }
        # xsi <- xsi + w_accel *(xsi - oldxsi )
        xsi <- xsi + w_accel *(xsi - parm_history[,3] )
        parm_history[,1:2] <- parm_history[,2:3]
        parm_history[,3] <- xsi
        xsi_change <- cbind( parm_history[,2] - parm_history[,1],
                                parm_history[,3] - parm_history[,2] )
        lam <- eucl_norm( xsi_change[ind,2] )/ ( eucl_norm( xsi_change[ind,1] ) + eps )
        if ( iter > itermin ){
            w_accel <- lam / ( 2 - lam )
            if ( w_accel > 10 ){
                w_accel <- 10
            }
        }
        xsi_acceleration$w <- w_accel
    }
    #*****************************************************
    # acceleration method of Ramsay (1975)
    if ( xsi_acceleration$acceleration=="Ramsay"){
        thre1 <- -5
        # use code from mirt package (author Phil Chalmers)
        dX2 <- parm_history[ind,3] - parm_history[ind,2]
        dX <- xsi[ind] - parm_history[ind,3]
        d2X2 <- dX - dX2
        ratio <- eucl_norm( dX ) / ( eucl_norm( d2X2 ) + eps )
        accel <- 1 - ratio
        if(accel < thre1){
            accel <- thre1
        }
        if ( iter > itermin ){
            xsi <- (1 - accel) * xsi + accel * parm_history[,3]
        }
        parm_history[,1:2] <- parm_history[,2:3]
        parm_history[,3] <- xsi
        if ( iter > itermin ){
            xsi_acceleration$beta_old <- accel
        }
    }
    #**************************************************************
    xsi_acceleration$parm_history <- parm_history
    xsi_acceleration$parm <- xsi
    return(xsi_acceleration)
}
#####################################################################
accelerate_parameters <- tam_accelerate_parameters


######################################################################
# Euclidean norm of a vector
eucl_norm <- function(x)
{
    sqrt( sum( x^2 ) )
}
######################################################################
# Euclidean distance of two vectors
eucl_distance <- function( x, y=NULL )
{
    if ( is.matrix(x) ){
        y <- x[,2]
        x <- x[,1]
    }
    eucl_norm( x - y )
}
######################################################################