Troubleshooting File Reads in MatNWB

Outlined below are the most common issues reported by users when they read a NWB file as well as common troubleshooting approaches to resolve them.

Schema Version Conflicts

If you run into an error where reading a file appears to expect the wrong properties, you should first check if your MATLAB path is not pointing to other environments with the same packages. MATLAB’s internal which command to check for unexpected class locations.

Multiple Schema Environments

By default, MatNWB generates all class files in its own installation directory. However, if your work requires you to manipulate multiple different schema versions or extension environments, you may want to generate the class files in a local directory so that MATLAB will default to those classes instead.

To do this, you can use the optional savedir keyword argument with nwbRead which allows you to specify a directory location within which your generated class files will be saved.

nwb = nwbRead('/path/to/matnwb/file.nwb', 'savedir', '.'); % write class files to current working directory.


Other generation functions generateCore and generateExtension also support the savedir option.

Missing Embedded Schemata

Some older NWB files do not have an embedded schema. To read from these files you will need the API generation functions generateCore and generateExtension to generate the class files before calling nwbRead on them. You can also use the utility function util.getSchemaVersion to retrieve the correct Core schema for the file you are trying to read:

schemaVersion = util.getSchemaVersion('/path/to/matnwb/file.nwb');

Avoiding Class Regeneration

If you wish to read your file multiple times, you may not want to regenerate your files every time since you know that your current environment is correct. For this case, you can use nwbRead’s optional argument ignorecache which will ignore the embedded schema and attempt to read your file with the class files accessible from your MATLAB path or current working directory.

nwb = nwbRead('path/to/matnwb/file.nwb', 'ignorecache');

Bottom of the Barrel

If you’re here, you’ve probably reached your wit’s end and wish for more specific help. In such times, you can always contact the NWB team either as a message on our NWB HelpDesk, Slack Workspace or as an issue on Github.