What is fitting? Suppose that you have a table of numbers, Y_{i}
and X_{i}, i=0..n. Then suppose that you have model representation
for these numeric Y(X) data: Y=f(X,p_{j}), j=1..m, and you want to find
numeric values of p_{j} that made table-defined curve Y_{i}( X_{i})
and model curve Y=f(X,p_{j}) most similar. This process is known as fitting.
If model function has linear dependence on fitting parameters, this can be
treated as linear fitting, otherwise you will have non-linear
fitting problem.

Linear fitting has more limited applications than NLSF.
However, it is much more fast and straightforward and does not require initial
parameter evaluations. This feature makes it more convenient for various
automatic fitting routines (see IDMApplication
interface for more details). Unfortunately linear fitting method has serious
restriction: you can fit only several predefined model functions (or function classes).

How to use Linear fitter? First you
should plot data to be
processed (this tool works only with active plot serie). Then make plot active and select
Process|Linear Fit menu item to display Linear Fitter window. You will
see your curve on the separate plot. Just select desirable fitting expression
from the list and click "Fit" button to create and show best fit curve.

In DM2000 you have a wide set of options that allows you to have full
control over the fitting process.

Zoom / UnZoom / Rescale - use these buttons to control
plot scale.

Select - you can fit only points whose coordinates belong selected
rectangular plot region.

Fitting equation - select desirable expression from the list. For some
expressions you should additionally define the number of terms in the
expression.

Fit - click this button to perform fitting and calculate parameter values.

When you click OK button, you may save fitting results in several ways:
copy fit curve to selected serie, add fitting results to the Notes
window, add parameter set to the selected worksheet
and create additional column with the fit curve in the worksheet referenced
by fitted serie.

Notice: if active serie (curve to be fitted) has nonempty X, Y
expressions, fit calculation algorithm will take these expressions into
account. In another words, transformed curve will be fitted. However, axis
expressions will be simply ignored (and you get warning message).