Smoothing a Variogram with Lag Width
On the variogram properties Experimental page, when the associated Auto check box is not checked, the Lag Width may be independently specified. In this case, the Lag Width is not a function of the Max lag distance and the Number of Lags. This flexibility allows for overlapping lag intervals and, therefore, a smoothed experimental variogram.
For example, consider the case where the Max lag distance is 100, the Number of Lags is five, and the Lag Width is 40. The resulting lag intervals would be 0 to 40, 10 to 50, 30 to 70, 50 to 90, and 60 to 100. Notice these intervals overlap. Overlapping lag intervals causes a moving average type smoothing of the experimental variogram. Often, it is easier to select an appropriate model for such smoothed experimental variograms.
In either case, the formulae for determining the intervals are given by the following pseudo-code fragment.
for(lag = 0; lag Number of Lags; ++lag )
{
center = Max Lag Distance / Number of Lags * (lag+0.5);
from = max( center - ( Lag Width / 2.0 ), 0.0 );
to = min( center + ( Lag Width / 2.0 ), Max Lag Distance );
}