Making a program recursive

Hi, I wonder if anyone may be able to help. I have a program I've written that is a sliding window, it basically sends chunks of data from(sample3) within the window to a function (grey_model_sw), this function outputs the variables [x,xs,yw]. Within the function, I have a variable t_test which at present is set manually to say 5000. What I would like to do is set t_test with the length of the last value to yw instead of having to set it manually. I have tried but failed to get this to work, any idea?

Help would be gratefully be appreciated.

Andy

Answer 1

[Salaheddin Hosseinzadeh]

Hi Andy!

I'm not sure if I understood your problem, so let me explain what I understood first! And if it is not what you mean please explain a little bit more.

My understanding: You have a function that you pass variables to and you get some outputs out of it. You have a parameter fixed inside your function to 5000 which should be length of the previous out put of the same function

For instance

[x,xs,yw] = myfunction(input1,in2,in3)
    % here you have some codes
    t_test = 5000;
    % rest of yoru code
    % assigning the output variables for example
    x  = sin(input1);
    xs = cos(in2);
    yw = tan(in2);
end % this is the end of the function

but you want your function to be as

[x,xs,yw] = myfunction(input1,in2,in3,t_test)
    % there is no constant t_test in body of the code
end

where t_test is = length(yw) of the last iteration!

So you can either put myfunction inside a loop and put this all inside another function if you like.

Or

Use a persistent variable! this variable does not remove when function is reached the end, so in the next iteration it has a value. Look at MATLAB help for persistent keyword.

I think your code should look like this eventually

[x,xs,yw] = myfunction(input1,in2,in3,in4)
    % here you have some codes
    %
    if ~exist(t_test)
       persistent t_test; defining a persistent variable
       t_test = in4; this only happens the first time
    end
    % rest of yoru code
    % assigning the output variables for example
    x  = sin(input1);
    xs = cos(in2);
    yw = tan(in2);
    %
    t_test = length(yw); here is setting the t_test for new iteration
    %
end % this is the end of the function

This is a clue on how to do it, I'm sure you can figure it out.

Good Luck!

[Andrew Wileman]

Brilliant, seems to work. I would have never thought of doing it like that. Many thanks Salaheddin.