Try to use a filename with .gz extension – this will use GZIPOutputStream instead of ZipOutputStream to compress the data, and perhaps it will solve the problem. If not, split your data into 2 separate parts and save/load them separately.

Thanks Yair, and sorry I’ve not been warned of your answer.

I’m facing again the issue, even when increasing this Matlab setting to its maximum (8,159Mb). I guess the issue is completely independent from the savezip function right? Is there a way to use another type of memory allowing to save such a big file without relying on Matlab’s internal java memory limit?

You can try to increase the Java heap memory size in the Matlab preferences (General => Java Heap Memory). Any changes to the settings will only take effect after restarting Matlab.
https://www.mathworks.com/help/matlab/matlab_external/java-heap-memory-preferences.html

Error using java.util.zip.ZipOutputStream/write
MATLAB array exceeds an internal Java limit.
Error in savezip (line 90)
    zos.write(dataInBytes, 0, numel(dataInBytes)); 

Would you have an idea how the internal java memory limit can be increased?

Thanks for clarifying. That’s what I guessed. However, it is possible in Java to read and write into or out of a gzipped csv-file in the format of old-school spreadsheet (e.g. Excel-compatible). So shouldn’t it be possible with MatLab via Java too? Perhaps that would require to mimick the “writetable” somehow. Unfortunately I currently dont have the time to continue with this, but it would still be super great, if someone figures this out.

You will need to manually extract your data into CSV format from Matlab’s table object. There is no direct way of doing that other than using writetable.

Dear Yair,

thanks for the quick response. Your code works perfectly fine. My problem is, that the file written is a gzipped mat-file. At least, if I uncompress it with some other program than matlab, I cannot interpret it easily. For a specific application, I need to have a gzipped csv-file (table). That means, if I gunzip it with some other program, it should give a common csv-file. Now, I guess that is possible with your code. But I don’t understand how. Could you please give an example? This would really be helpful and boost my performance a lot.

Thanks again.

@Holger – read the article carefully: I explained how you can serialize any Matlab data (including tables) into a byte stream that can then be compressed into a zip/gz file. You can use the savezip utility for this as explained in the article.

Would you know a way to write a table directly to a zip/gz-file instead of writetable() to csv and subsequenly compressing it? As far as I know, in Java that’s possible.

Any help is greatly appreciated.

>> b = zip(a);
>> a = unzip(b);

>> whos a b
  Name         Size                 Bytes  Class    Attributes
  a         1024x1024             1048576  uint8              
  b            1x65536              65536  uint8  

This could be an invaluable tool when we want to keep in memory large amount of redundant data for maximum speed data access, e.g. picking rapidly images from thousands-of-images-database, which exceed the size of memory when it’s uncompressed.