I am getting this preallocation warning

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Vânia Gonçalves
Vânia Gonçalves on 19 Nov 2022
Commented: Jan on 19 Nov 2022
  5 Comments
Vânia Gonçalves
Vânia Gonçalves on 19 Nov 2022
hi
i already searched in the internet, but i didn´t find any usefull explanation, so i hoped find help here.
but thanks anyawy

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Answers (2)

Steven Lord
Steven Lord on 19 Nov 2022
This is a Code Analyzer warning not a run-time warning.
If you're not sure what preallocation is, why it can be important, or how to do it see the first example on this documentation page.

Jan
Jan on 19 Nov 2022
Moved: Jan on 19 Nov 2022
Seriously? If I ask Google, I get e.g.:
For your code:
...
maxIter = 1000;
x = zeros(maxIter, 1);
y = zeros(maxIter, 1);
while norm(J) > e && i < maxIter
...
end
x = x(1:i); % Crop unused elements
y = y(1:i);
  2 Comments
Jan
Jan on 19 Nov 2022
What does "long" mean? Seconds or hours?
Symbolic calculations need some time. You can use the profiler to find the bottleneck:
doc profile

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