MATLAB: How do you load corrupt “v4” MAT files that produce error on using “load”

corruptloadmatfileMATLABv4

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MAT files have restrictions on their structure based on the specific version of the MAT file being used. In the specific case of the "v4" version, the maximum number of elements in an array cannot exceed 100000000, and the size of each individual variable cannot exceed 2 GB as listed here:

https://www.mathworks.com/help/matlab/import_export/mat-file-versions.html#btij555

If the load function shows errors regarding corrupt v4 files format, here are some possible workarounds you can try in order to resolve the issue:

1. It is possible that the file might be corrupted during the generation process. Please regenerate the file and try loading again to make sure that it is not the case.

2. Try loading specific variables from the existing v4 MAT file and then save all the variables into a new MAT file in the latest version. I have attached a script called "partial_load_save.m" which uses the "whos" command to figure out the variable names in the original v4 MAT file and then loads them into MATLAB one by one using a "for" loop and then saves the variables in the workspace into a new MAT file in the latest MAT file version.

You can learn more about the "whos" command and loading specific variables from a "matfile" in the following links:

https://www.mathworks.com/help/matlab/ref/whos.html#bu22jzs-4

https://www.mathworks.com/help/matlab/ref/load.html#btm0etn-5

Related Solutions

MATLAB: How to load a single variable from a structure

If you have many variables in a MAT file, among which the structure of interest is also contained, there is no way to load only a single member of this structure into the workspace. For example, consider the following contents in the MAT file "sample.mat":

var1
var2
var3
structureVar

where "structureVar" contains the following:

sVar1
sVar2

Say we would like to load only "sVar1" into our workspace from "sample.mat". Currently, there is no way to do this. This is described in the "Limitations" section of the "matfile" documentation.

https://www.mathworks.com/help/matlab/ref/matfile.html#bt2ft8s-6

A workaround is to save the structure as an independent MAT file, and load members of the structure as needed. This is documented in "Variables" section of the "save" documentation:

https://www.mathworks.com/help/matlab/ref/save.html#btox10b-1-variables

For example, save "structureVar" as "structureVarMatFile.mat" when it is in the workspace using the following command:

>> save('structureVarMatFile','-struct','structureVar');

Now, you can load only "sVar1" if needed, using the following command:

>> load('structureVarMatFile','sVar1');

MATLAB: Loading large MAT files which are saved using “Save As” in Workspace gives error “File is corrupt”

When you right click a variable in MATLAB Workspace and click "Save As", MATLAB runs the saving process in the background. Since the process is running in the background, we would have no way to know if the process is completed or not.

Loading a MAT file which is still being saved in the background or which was interrupted half way through because of closing MATLAB, results in the error.

Instead of using "Save As" in MATLAB Workspace, you can work around this issue by using the "save" command from the MATLAB Command Window.

For example, if you want to save the variable "April8Data" in the file "April8Data.mat" use the following command:

>>save('April8Data.mat', 'April8Data', '-v7.3')

Also be sure to use the '-v7.3' flag when your variable size is >2GB.

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Related Solutions

MATLAB: How to load a single variable from a structure

MATLAB: Loading large MAT files which are saved using “Save As” in Workspace gives error “File is corrupt”

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