This variable is read from, but it hasn't been declared yet. Example:
z = x
where x is the undeclared variable. Variables are declared when they are first written to. In this case, x is auto-declared and given the value (0,0), and its type is complex. However, this warning indicates a logical error in the formula.
This would be a possible solution for the example given above:
float x ... z = x
See Also
Warnings