How do I append data to a MAT file from C++?

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flybyya23 2015-6-25

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评论： shuangshuang kong 2018-4-15

From a C++ program, I would like to continuously append data to a MAT file while the program runs. The program doesn't have to append to an existing file, but after creating the file at the beginning the program needs to append save data to the MAT file over long periods of time. mxCreateNumericMatrix appears to require the size of the variable to be known with no options to append. The program cannot keep all the data in memory and then write it upon completion.

Thanks!

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shuangshuang kong 2018-4-15

have you solve this problem yet? can you tell me how to do?because i have also met such problem,and i dont know how to figure it out.

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Answer 1

James Tursa 2015-6-30

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Why does it have to be a mat file? The simplest solution is to simply write the values in binary as you go, and then when you are done close the file. Then in MATLAB use fopen and fread to read in the data (in pieces if necessary because of memory constraints).

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flybyya23 2015-7-1

I was attempting to use a MAT file only because I assume MATLAB has optimized loading these files and multiple variables are named/segregated when stored/loaded. This may be my only and best choice though (use my own binary format) if MATLAB/API doesn't support what I need ... I'm surprised it wouldn't allow you to do this.

James Tursa 2015-7-1

MATLAB compresses mat files ... maybe that is what you mean by "optimized loading".

Is it your desire to write a MATLAB variable to a mat file incrementally without specifying the size, and then at the end specify the size of the variable? And do this for several variables in the same mat file?

If the variable can't be held in memory at once, is it your plan to load only pieces of it later?

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Answer 2

Adam Hug 2015-6-30

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I think your best bet will be to use MATLAB Engine. This is an API that lets you run MATLAB commands using C/Fortran programs. See the following doc link for more information and examples:

http://www.mathworks.com/help/matlab/calling-matlab-engine-from-c-c-and-fortran-programs.html