Declaring a vector in matlab whose size we don't know

Suppose we are running an infinite for loop in MATLAB, and we want to store the iterative values in a vector. How can we declare the vector without knowing the size of it?

z=??
for i=1:inf
    z(i,1)=i;
    if(condition)%%condition is met then break out of the loop
        break;
    end;
end;

Please note first that this is bad practise, and you should preallocate where possible.

That being said, using the end keyword is the best option for extending arrays by a single element:

z = [];
for ii = 1:x
    z(end+1, 1) = ii; % Index to the (end+1)th position, extending the array
end

You can also concatenate results from previous iterations, this tends to be slower since you have the assignment variable on both sides of the equals operator

z = [];
for ii = 1:x
    z = [z; ii];
end

Sadar commented that directly indexing out of bounds (as other answers are suggesting) is depreciated by MathWorks, I'm not sure on a source for this.

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If your condition computation is separate from the output computation, you could get the required size first

k = 0;
while ~condition
    condition = true; % evaluate the condition here
    k = k + 1;
end

z = zeros( k, 1 ); % now we can pre-allocate
for ii = 1:k
    z(ii) = ii; % assign values
end