Uploading .mat files that contain nested structs into a datastore

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I would like to upload .mat file into a datastore that contains nested structs. Like so...
TestData.Unit1.Parameter 1
TestData.Unit1.Parameter 2
TestData.Unit2.Parameter 1
TestData.Unit2.Parameter 2
When I try to upload this into a datastore I cannot read the content of the fields inside the nested struct. The size of the .mat files are enormous and take a really long time to load one parameter. How do I accomplish this while still using datastore or something of the like? I know we are supposed to use fileDataStore to create the custom read function but the read function I created only displays the first level of the structs.
Matt J
Matt J on 20 Feb 2024
Edited: Matt J on 20 Feb 2024
When you say "upload" do you truly mean that the datastore reads from files stored on a remote computer? If so, maybe the reading time is predominantly due to the remote connection, rather than the file size.
Dennan on 20 Feb 2024
It is files stored on a network of computers. So there is no way to "point" to the data and call specific parameters as needed?

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Accepted Answer

Catalytic on 20 Feb 2024
Edited: Catalytic on 20 Feb 2024
I think the wisest course would be to reorganize your data and assign each "Unit" to its own separate .mat file.
Matt J
Matt J on 20 Feb 2024
It wouldn't matter if the data is write-protected. You could read the data, reorganize it, and copy the reorganized data somewhere controlled by you and where you would have full read/write acess.
If for some reason you can't do that, so be it. However, one of the upsides of @Catalytic's suggestion is that if you split the data this way, you could shuffle the Parameter instances. In the form you have things now, the shuffle() command can only vary the the read-out order of the files, not the order of the Parameters within the files.

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More Answers (1)

Matt J
Matt J on 20 Feb 2024
This example shows how to use a fileDataStore to read partial data from a .mat file
I might modify their example and use a matfile object to read the data without actually loading the entire file.
Stephen23 on 21 Feb 2024
Edited: Stephen23 on 21 Feb 2024
"How do you get to the actual data within the struct?"
Based on what you show in your comment, perhaps something like this:
S = read(fds);
Matt J
Matt J on 21 Feb 2024
Based on what you show in your comment, perhaps something like this:
Yes, but the OP would like the read() operation to return this directly.

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