Use older MATLAB save formats

Question

Lauren Dransfield 2019-2-12

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评论： Rik 2019-2-12

I'm running a model that has a bunch of DLLs which read some .mat files.

When I use an old version of MATLAB (I think 2011a) to generate the files I get files that work okay, but when I create them with 2017a the files seem not to work with the same script.

I've used 2017 to read in the working 2011 file and then save it, and these files also don't work.

I've also tried the above with the '-vXX' settings at all available values according to the help, with no success.

Example:

clear; load('v2011file.mat'); save('v2017copy.mat', '-v6', 'var1', 'var2', 'var3');

One thing that I have notices between the two is that when they're selected in the "Current folder" browser, the preview always shows the 2017 files with the variable names in aphabetical order, regardless of the order that I saved them in, while the older 2011 file seems to maintain the order that they were saved. I can only assume that this is something related to a change in the way that files are saves - it might not be a problem but it does hint toward a change (it does this whether or not I include '-vXX' to use older formats).

It's probably worth noting that the 2011 files are created on XP, while the 2017 files are made on Windows 7.

Essentially I'm looking for anyone who might know whether it's possible for me to change the way that the file is put together by MATLAB, rather than having to change the DLLs to acceps a newer file.

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Stephen23 2019-2-12

编辑：Stephen23 2019-2-12

The "order" of variables stored in a .mat file should not be relied upon, and code that assumes that they come in a particular order is fragile code.

Having the variables in a particular "order" implies that they have some meta-data in their names (i.e. pseudo-indices), which is a slow and inefficient way to handle meta-data: much more robust would be use use actual indexing (in which case this entire problem disappears).

Lauren Dransfield 2019-2-12

I don't disagree, it's not very robust at all and isn't how I'd have done it myself (it goes so far as insiting that each matrix and vector is a specific size, which is completely inappropriate).

These are largely scripts that I've inherited and don't have time to fix before results are required, and so finding a workaround for the timebeing is better this time around.

I'll take your comments into account next time I have time to update the code to something a bit more robust, thanks.

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Answer 1

Lauren Dransfield 2019-2-12

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https://ww2.mathworks.cn/matlabcentral/answers/444507-use-older-matlab-save-formats#answer_360655

编辑：Lauren Dransfield 2019-2-12

It looks like I can work around the save order issue and have something that works by doing:

save('new2017file.mat', 'var1');
save('new2017file.mat', 'var3'. '-append');
save('new2017file.mat', 'var2', '-append');

Meaning I can put them in a specific order - I have to have the default save set to -v7 in preferences>general>.mat files too.

I wouldn't say no to a more elegant answer if there's one available though!

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Answer 2

Rik 2019-2-12

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https://ww2.mathworks.cn/matlabcentral/answers/444507-use-older-matlab-save-formats#answer_360660

在 MATLAB Online 中打开

Since v7.3 is R2006b, I don't really see a reason why you would need to set the default to -v7.

Also, why don't you write a wrapper to replace the load? That way you remove the ordering requirement, without having to do a lot of work.

function S=loaddata(filename)
tmp=load(filename);
S=struct('var1',tmp.var1,'var2',tmp.var2,'var3',tmp.var3)
end

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Lauren Dransfield 2019-2-12

Looks like it'd be a better way to have it in future, but I'm not sure the DLLs will be happy trying to read a structure when it isn't what they're expecting