SetFormula
SetFormula waveOrVariableName, expressionStr
The SetFormula operation binds the named wave, numeric or string variable to the expression or, if the expression is "", unbinds it from any previous expression. In user functions, SetFormula must be used to create dependencies.
Parameters
expressionStr is a string containing a numeric or string expression, depending on the type of the bound object.
Pass an empty string ("") for expressionStr to clear any previous dependency expression associated with the wave or variable.
Details
The dependent object (the wave or variable) will depend on the objects referenced in the string expression. The expression will be reevaluated any time an object referred to in the expression is modified.
Besides being set from a string expression this differs from just typing:
name := expression
in that syntax errors in expressionStr are not reported and are not fatal. You just end up with a dependency assignment that is marked as needing to be recompiled. The recompilation will be attempted every time an object is created or when the procedure window is recompiled.
Use the Object Status dialog in the Misc menu to check up on dependent objects.
Examples
This command makes the variable v_sally dependent on the user-defined function anotherFunction, waves wave_fred and wave_sue, and the system variable K2:
SetFormula v_sally, "anotherFunction(wave_fred[1]) + wave_sue[0] + K2"
This is equivalent to:
v_sally := anotherFunction(wave_fred[1]) + wave_sue[0] + K2
except that no error will be generated for the SetFormula if, for instance, wave_fred does not exist.
A string variable dependency can be created by a command such as:
SetFormula myStringVar, "note(wave_joe)"
observe that expressionStr is a string containing a string expression, and that:
SetFormula myStringVar,note(wave_joe)
is not the same thing. In this case the note of wave_joe would contain the expression that myStringVar would depend on! Also, wave_joe would have to exist for Igor to understand the statement.