Variables

A Variables object is used to add named dummy parameters that are used to constrain fits.

To create the object, right click on the Mixture or Overlays object and select "Add New...,Variables".
To create a parameter, right click on the Variables object and select "Add Parameter...".
To delete a parameter, right click on the parameter and select "Remove Parameter(s)"
To rename a parameter, right click on the parameter and select "Rename Parameter".

This is particularly designed for force field analysis (see z matrix for an example) but can be useful in other contexts. For example, to fit to a band origin and a separation, rather then two band origins, add a parameter named "Offset" as above, and then add a constraint along the lines of:

Constrain NH3.ND2H.B.A2.Origin := Variables.Offset + NH3.ND2H.B.B1.Origin

With this set up the new parameter, effectively the difference between the two origins, and one of the origins (NH3.ND2H.B.B1.Origin) are floated, rather than both origins. Also see the FrequencyOffset and FrequencyScale directives, which can specify a variable, rather than a constant value.

Settings

Global If true, then variables given in this object are available in all expressions. (If false, then the values will require specifying the full name, as Variables.Offset above.)