MATLAB: Is there any way to load parts of a large table from a mat-file

matfilesubindexingtable

I a trying to load parts of a very large table using subindexing.

f=matfile(fileName);
sub=f.X(1:10,:);

I get the following error: The variable 'X' is of class 'table'. To use 'X', load the entire variable. Why? Should I store tables in a different format than matfiles?

Best Answer

This is one of the documented limitations of the matfile object.

" matfile does not support indexing into:

Variables of tables"

Since you're working with data that's too big to fit in memory, you should explore if tall arrays satisfy your needs. You can create tall table arrays as shown in the "Creating Tall Tables" section of that documentation page.

Related Solutions

MATLAB: Reading variables from a big matlab Table

Yes, matfile won't help since it can't partially load a table.

Unfortunately, as you are now there is no workaround I'm aware of. You could always contact Mathworks support directly to see if they have a solution.

If the data is to be accessed more than once, then what I'd do is convert all these tables to Tall Tables, then save them with the write function. As far as I know there is no way to convert a regular mat file to one compatible with tall arrays so You'd have to take the performance hit once when you load the tables for the first time as regular table, but subsequent loads would allow you efficiently load only the data your require as you'd be using tall arrays.

MATLAB: How to recover data from a corrupt MAT-file

The issue might be caused by the presence of a corrupt zero-byte tag in the MAT-file. If this is the case, one might be able to extract the data from the MAT-file until a corrupt zero-byte tag is reached.

Please download the following SPLITMAT file in your current folder of MATLAB. Also, please ensure that the corruptMATFile is in the same current folder.

Then use the command as detailed below:

splitmat corruptMATFileName % Do not include the .mat extension

The above command will generate "n" MAT-files: corruptMATFileName_1.mat through corruptMATFileName_n.mat, each containing a variable contained in the original MAT-file.

If this command does not work, you may also try the following syntax to recover non-corrupted variables from the MAT-file:

>> load('<corrupted_file>.mat', '<uncorrupted_variable>');

Best Answer

Related Solutions

MATLAB: Reading variables from a big matlab Table

MATLAB: How to recover data from a corrupt MAT-file

Related Question