MATLAB: How to make an object declared within a function persistent

Question

I have defined two handle classes for audio filters (LPcomb and APfilt). I would like to write a function to apply these filters to streaming audio on a block-by-block basis. So I declare the object variables to be persistent. In the "if isempty – end" block I try to instantiate these variables as objects of my classes. I get the following error message:

The following error occurred
converting from LPcomb to double:
Error using double
Conversion to double from LPcomb
is not possible.

So it seems that when you declare a variable to be persistent, it is declared as a double and cannot be instantiated as an object. How can I declare persistent objects in a function?

Answer 1

As Guillaume notes, we'll need the code in question to help you further.

However, it is important to note that persistent variables are initialized as double arrays so a type change must first be performed if you would like the persistent variable to store non-double elements, as discussed in this answer: Trouble with persistent array of class objects