How can I make an object declared within a function persistent?

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Warren Koontz
Warren Koontz 2015-6-16
评论： Warren Koontz 2015-6-17
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?

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Eric Lin
Eric Lin 2015-6-17
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
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Warren Koontz
Warren Koontz 2015-6-17
Thanks. The information in the link you provided fixed the problem. Here is a partial listing of the "before" code:
comb(Nc)=LPcomb;
for n=1:Ncf
comb(n)=LPcomb(cfDelay(n),damp,fbck);
end
Here is the same code "after"
comb=LPcomb;
for n=1:Ncf
comb(n)=LPcomb(cfDelay(n),damp,fbck);
end
In both cases, comb and Nc are persistent. No error message for the "after" version and the function worked fine. I didn't even get the warning about dynamic allocation!
Thanks for your help.
PS - This OO version ran MUCH more slowly than its non-OO predecessor!

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