How do I load only part of a table saved to a .mat file?

I have some large tables stored in .mat files and was wondering if there is a way I could load only some of the data into MATLAB (for example, a subset of rows or columns in a table). I read about the matfile function, but it doesn't seem to work with tables. Whenever I try to load part of a table, I get an error telling me to load the whole table. Is there some way to load partial data that works for tables?

Answer 1

[Kyle Padilla]

I found out you can make your table a tall table, which provides a way to work with large amounts of data. You use the tall function and pass in your table. You can write your table to a folder of .mat files using the write function. You then create a datastore and convert it to a tall table. Finally, you can get a subset of the tall table and use the gather function to get the results.

There is an example in the MATLAB documentation: https://www.mathworks.com/help/matlab/ref/matlab.io.datastore.talldatastore.html

Answer 2

[Walter Roberson]

No, there is no method provided for that.

Answer 3

[Peter Perkins]

You might look into using datastores, which would, in effect, allow you to load pieces.

[Kyle Padilla]

I found tabularTextDatastore, but it doesn't seem to work with .mat files. It looks like you might be able to use fileDatastore to do it, but I haven't figured out how to write the read function yet. Thanks for the suggestion.

[Walter Roberson]

@Kyle Padilla

I believe that the idea is that if the table were instead stored in a file such as a .xlsx file, then tabularDataStore would be able to process it piecewise, chunks of rows at a time.

[Kyle Padilla]

@Walter Roberson

That might work yeah. I think I figured it how I can do this with .mat files though. Gonna post an answer to my question so others can use it for future reference.