Stanford Research Systems SR850 User Manual page 145

Fit
Do Fit:
Type of Fit
Line Exp
Gauss
View
Params:
Limits
Left:
Right:
Return:
Do Fit
Type of Fit
View Parameters
The Fit sub menu allows the user to fit one of three curves to the data
within the active chart display - lines, exponentials, and Gaussians. Fit-
ting is done using the Marquardt 'Gradient-expansion' algorithm to mini-
mize chi-squared.
MATH
Fit
Pressing this key starts the actual fit calculations. While calculations are
in progress, the "Calculating fit..." message is displayed at the bottom of
the screen. The algorithm is designed to iterate until the change in chi-
squared falls below 0.1%, although the fit may be terminated at any time
by pressing the Abort (Return) softkey. The value of chi-squared is
shown after each iteration.
When the fit terminates, the best fit curve is plotted and the parameters
of the fit are displayed in a window at the center of the screen. Pressing
any key to continue will remove the parameter window while leaving the
best fit curve on the display. Pressing another key to continue will
remove the curve and restore the graph to normal. See View Parameters
below for a description of each fit.
This function toggles the Type of Fit between line, exponential, and
Gaussian. The fit takes place only within the fit region defined by the Left
and Right Limits (see below) on the active chart graph.
The View Parameters function displays the most recent curve fit and
parameter window. For example, if a fit was performed and then the Fit
menu exited, the fit will be erased from the screen. If the graph is then
scaled differently using the Display Scale menu and then the Fit menu
5-35
Do Fit
Fit Type
View Parameters
Left Limit
Right Limit
Return
Math Menu
Abort