Saving data from loop

Question

hi hey 2018-1-21

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/378179-saving-data-from-loop

评论： hi hey 2018-1-21

while(run<time)

    if(run > time)
       break
    end
~do calculations~

z=[];

pie= crust*apple;

z=[pie];

~do calculations~

end

I'm trying to store all of the calculations from pie but for some reason it is being overwritten each time it goes through the loop. what else would I need to add to have the data saved correctly?

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Answer 1

Stephen23 2018-1-21

0
链接

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https://ww2.mathworks.cn/matlabcentral/answers/378179-saving-data-from-loop#answer_301048

编辑：Stephen23 2018-1-21

在 MATLAB Online 中打开

method one: concatentation:

z = [];
while ...
   ...
   pie = ...
   z = [z,pie];
end

method two: indexing:

replace z = [z,pie] with:

z(end+1) = pie;

Note that expanding z on each iteration will be very inefficient, and will likely slow down your code: it is rarely a good idea to start with an empty array and enlarge it on each loop iteration. See:

https://www.mathworks.com/help/matlab/matlab_prog/preallocating-arrays.html

https://blogs.mathworks.com/loren/2012/11/29/understanding-array-preallocation/