Save loop variable naming problem

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peter huang 2022-8-30

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评论： Stephen23 2022-8-31

I want to save the answers in the loop for future use, I understand that I can use sprintf to batch store the data in the variables, but if I want to change my name with the loop, how can I do it?

ex.

for i = 1:10
    k(i) = 2^i
end

k =

2 4 8 16 32 64 128 256 512 1024

I want to name the variables separately as

k1 = 2
k2 = 4
k3 = 8
....
k10 = 1024

回答（1 个）

Image Analyst 2022-8-30

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Please don't do that. It's a bad idea. Why not do it? See the FAQ:

https://matlab.fandom.com/wiki/FAQ#How_can_I_create_variables_A1,_A2,...,_A10_in_a_loop?

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Image Analyst 2022-8-30

在 MATLAB Online 中打开

You "solved" your problem in a bad way - they way we explicitly told you not to do:

eval(['moving_time_' num2str(i) '=plot_time;']);

First of all, if you have just a handful of variables, like 4 or less, it's fine to have separately named variables but just assign them immediately, by their known name, rather than in a loop and by using the hated eval().

However, if you have a large or variable number of variables, then create a 2-D array if they're all the same size, or a cell array if they (unfortunately) need to be of different lengths. For example

numVectors = 10; % or whatever it is.
moving_time = zeros(numVectors, vectorLength); % Preallocate space in advance.
for k = 1 : numVectors
    thisMoving_time = plot_time; % Get the plot times for this iteration somehow.
    moving_time(k, :) = thisMoving_time; % Store this time vector as row k of our 2-D array
end
% Save the 2-D array of all time vectors as a single variable in a single .mat file.
fullFileName = fullfile(pwd, 'moving_times.mat'); 
save(fullFileName, 'moving_time');  

peter huang 2022-8-31

Great, I think this method is much better than eval Then I would like to ask how the variable I want to access today is not 1*n, but may have 68*n and then 20 years of data every year.

Stephen23 2022-8-31

https://www.mathworks.com/help/matlab/timetables.html

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