MATLAB: My MATLAB keeps reading old .mat files as uint32 even though it ain’t, why is it and how can I fix this

MATLABoop

I thought of upgrading/updating my MATLAB, might that fix the issue?
Why is it happening in the first place?
As in:
load(data_set_path);
then if it had saved a struct there is doesn't return it but reads it as uint32 and throws error:
Warning: Variable 'data4cv' originally saved as a cross_validation_data
cannot be instantiated as an object and will be read in as a uint32. 
> In pca_train (line 5)

Best Answer

You saved one or more objects in the MAT-file, but the definition for the object's class is not available to MATLAB when it loads the data so it doesn't know how to convert the raw data from the MAT-file into an instance of the object.
Try to remember if you were using any third-party toolboxes when you created that MAT-file. If so, check if they are still accessible to MATLAB. I'm betting that you were using such a toolbox but it is no longer available to MATLAB when you try to LOAD the file.
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