R/tam_pv_sampling_beta.R

In TAM: Test Analysis Modules

## File Name: tam_pv_sampling_beta.R
## File Version: 0.13

tam_pv_sampling_beta <- function( theta1, ndim, Y, pweights, eps=1E-8 )
{
    # bootstrap sample of persons to get sampled beta coefficients
    if ( ndim > 1 ){
        N <- nrow(theta1)
        ind <- sample( 1:N, N, replace=TRUE)
        theta1 <- theta1[ ind, ]
        Y1 <- Y[ ind,, drop=FALSE ]
    } else {
        N <- length(theta1)
        ind <- sample( 1:N, N, replace=TRUE)
        theta1 <- theta1[ ind ]
        Y1 <- Y[ ind,, drop=FALSE ]
    }

    #-- fit linear model
    modlm <- stats::lm( theta1 ~ -1 + as.matrix(Y1), weights=pweights[ind])
    beta <- modlm$coef            # sampled regression coefficients
    if ( sum( is.na(beta) ) >=0 ){
        C <- as.matrix(Y1)
        C1 <- crossprod(C)
        diag(C1) <- diag(C1)*(1 + eps)
        D <- crossprod(C, theta1 )
        beta <- solve(C1) %*% D
    }
    if ( ndim==1 ){
        beta <- matrix( beta, ncol=1 )
    }
    return(beta)
}