# matlab coder report Size mismatch (size [0 x 0] ~= size [1 x 2])

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zhou caiwei on 15 Aug 2022
Commented: Walter Roberson on 13 Feb 2023
I tried to use matlab coder to convert my matlab file into C\C++ source file. In my *.m file,I defined a dynamic array:
...
coord_list = [];
I_list = [];
...
for i=1:n
....
coordinate = yy;
I = zz;
coord_list = [coord_list;coordinate];
I_list = [I_list;I]
end
The error occurs like:
??? Size mismatch (size [0 x 0] ~= size [1 x 2]).
The size to the left is the size of the left-hand side of the assignment.
How could I fix this bug? how should I modify my matlab code so that It meets the requirements of C\C++ style for matlab-coder?
Chiluveru on 13 Feb 2023
hi Raghu,
I am alsp facing same issue like the error below:
Size mismatch (size [1 x 0] ~= size [16 x 0]).
need your help for solving it

Chunru on 15 Aug 2022
...
coord_list = zeros(n, m1); % m1 is the length of yy below
I_list = zeros(n, m2); % m2 is the lenght of zz
...
for i=1:n
....
coordinate = yy;
I = zz;
coord_list(i, :) = coordinate;
I_list(i, :) = I;
end
Bruno Luong on 17 Aug 2022
Edited: Bruno Luong on 17 Aug 2022
Your code is too long for me to look in detail. I notice that the code is not even optimized (growing array, call function in the loop, some common calculation is repeated, some constant quantity is computed inside the loop, etc...)
My recommendation is working on your matlab code before feed it to the coder.
zhou caiwei on 18 Aug 2022
you are right, I think I should optimize my code.Is there any reference materials?

Raghu Boggavarapu on 25 Aug 2022
Hi,
MATLAB Coder supports growing an array only by concatenation, growing an array by index is not supported. Please see: https://in.mathworks.com/help/coder/ug/limitations-with-variable-size-support-for-code-generation.html
If you wish to assign varying sized arrays to same variable, you can use coder.varize .
Also if you would like to optimize the MEX runtime, you can try disabling IntegrityChecks and ResponsivenessChecks in the MEX coder config.
##### 3 CommentsShow 1 older commentHide 1 older comment
Chiluveru on 13 Feb 2023
need help to solve the above error
Walter Roberson on 13 Feb 2023
You are assigning an empty array with 16 rows to a variable that was first assigned an empty array with one row.
When you use MATLAB Function Blocks in Simulink, then unless you use coder.varsize then the first assignment to a variable sets the limits on how large the variable is. This is different from regular MATLAB as regular MATLAB adjusts sizes as needed.

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