R/tam_acf_matrix.R

In TAM: Test Analysis Modules

## File Name: tam_acf_matrix.R
## File Version: 0.03


tam_acf_matrix <- function(x)
{
    # compute row-wise autocovariance
    # It corresponds to an autocorrelation if rows are standardized
    nx <- ncol(x)
    v1 <- rep(0, nrow(x) )
    if (nx > 1){
        for (nn in 2:nx){
            v1 <- x[,nn] * x[,nn-1]
        }
        v1 <- v1 / ( nx - 1)
    } else {
        v1 <- NA
    }
    return(v1)
}