Paste tab delimited reference data for R, M and S in the left hand pane and press the [Fit] button to perform the regression. This gives us four parameters for the fit: a, br, bm and the residual standard deviation σ. The [Null fit] button is used to simply calculate the mean and standard deviation of s, this can then be used to provide a model which ignores the dependency on mean ring width and number of heartwood rings. The [Stop] button can be used to stop a fit in progress. All statistical packages can also perform this fitting stage.
This tool can also calculate ranges from these parameters once they are calculated. To do this paste the test data into the left hand pane and press the [Test] button. This will calculate ranges and the proportion of sapwood rings falling within the expected range. This tool allows you to test a model on data where the number of sapwood rings is known.
The parameters can be entered and retrieved from the tool using the [Params>] and [<Params] buttons. Only the first four parameters are needed for the model.