Output argument "px" (and maybe others) not assigned during call to "function1"

Hi,

I am fairly acquainted with matlab, however failing to understand the output error I am getting from the following function.

function [px, b, c, d ,mse, varx] = function1 (x, y, h, i, j, k, l)

somecode

% Design Matrix 

Des_mat = X;

    while varx >= tol
        
        somecode
        b = vector; 
        w_mat = w; 
        c = w_mat; 
        d = scalervalue;
        [px,~,mse] = lscov(Des_mat,yn,w_mat.^2);                     % Evaluate lscov
        varx = 1.2;                                                 % some value
        somecode;
        

    end
    
end 

When this function is called in a for loop as

for l=1:k
    
    somecode; 
    
    [px, b, c, d ,mse, varx] = function1 (x, y, h, i, j, k, l);
    
    somecode;

end

It gives following error

Output argument "px" (and maybe others) not assigned during call to "function".

Surprisingly, the function

function1

runs for first 47 iterations. However, it fails to run afterwards. Can someone help and explain despite px being assigned why it is failing to execute?

Many Thanks

Answer 1

[Jan]

If the initial value of varx is smaller than tol already, the body of the while varx>=tol loop is not entered at all. Then e.g. px is not defined. Add a test of this condition:

if varx < tol
    error('Unexpected initial value');
end
while varx >= tol
    ...
end