15.3.4.4.4 The Variables and Parameters Page

This page offers options to allow you to specify variables and parameters for the fitting function. After the settings done in this page, you could go further to the next several pages to write fitting function body, fix parameters, write initialization codes etc.

Dialog Box Controls

When the function model is set to Explicit:

Independent Variables Input independent variables here. If you need to input multiple variables, please separate them using comma.
Dependent Variables Input dependent variables here. If you need to input multiple variables, please separate them using comma.
Parameters Input parameters here. If you need to input multiple parameters, please separate them using comma.
Derived Parameters Specify Derived Parameters here. Derived parameters are additional parameters to be computed from the function parameter values after the fitting process ends.
Constants Specify Constants here. Constants are fixed values that can be used either in the function expression or in parameter initialization code.
Peak Function Check this check box if you want to use your function for fitting peaks in the Peak Analyzer or for replica fitting in the NLFit tool.

Please note that parameters for peak function have special Peak Attributes that need to be set on the next page.The first parameter in the parameter list must be named as "y0" and should be assigned the peak attribute "offset". Besides "y0", you need to define at least three more parameters, and set peak attribute as "center", "width" and "amplitude/area". The following is an example of peak fitting function:

y = y0 + (2*A/PI)(w/(4*(x-xc)^2 + w^2))


When the function model is set to Implicit:

Variables Input independent variables here. If you need to input multiple variables, please separate them using comma.
Formula Number Input the number of f formula here. For formula number between 1 to 9, you could choose from the drop-down menu.
Estimates Output the name(s) of formula here. The names are automatically generated according to the Formula Number.
Parameters Same as the above table.
Derived Parameters Same as the above table.
Constants Same as the above table.
Peak Function Same as the above table.

You can also add, rename or delete the Parameters and Constants in the next setting page (the Function Body Page), see the tips at the end of the The Function Body Page.