[Mne_analysis] Problem exporting data from Matlab (Fieldtrip/SPM) for mne-python

[Nick Ward]

Hi.

I'm having trouble getting set of MEG data to load in Python (both 2 and 3).
I'm exporting the data from SPM by converting to Fieldtrip raw format
(spm2fieldtrip), and then calling fieldtrip2fiff.
I get a few warnings here, but the file is saved nonetheless:

> the input is raw data with 340 channels and 120 trials
> Warning: the data does not contain a trial definition
>   In utilities/private/warning_once at 158
>   In utilities/private/fixsampleinfo at 66
>   In ft_datatype_raw at 154
>  In ft_checkdata at 224
>   In fieldtrip2fiff at 57
>   In export at 8
> Warning: reconstructing sampleinfo by assuming that the trials are
consecutive > segments of a continuous recording
>  In utilities/private/warning_once at 158
>  In utilities/private/fixsampleinfo at 79
>  In ft_datatype_raw at 154
>  In ft_checkdata at 224
>  In fieldtrip2fiff at 57
>  In export at 8
> Reconstructing channel locations, it might be inaccurate
> Unknown channel type refmag, assigned to meggrad....

In Python I then try and load the data with mne.fiff.Raw('data.fif'), but
get an exception:

> /usr/lib/python2.7/site-packages/mne/fiff/raw.pyc in _read_raw_file(self,
fname, allow_maxshield, preload, compensation, verbose)
>     191             else:
>     192                 if len(raw_node) == 0:
> --> 193                     raise ValueError('No raw data in %s' % fname)
>     194
>     195         if len(raw_node) == 1:
> ValueError: No raw data in data.fif

I've inspected what is loaded in the debugger, and it appears as if the
file is being read. An exception is thrown however when there are no nodes
found in the meas structure containing FIFFB_RAW_DATA or
FIFFB_CONTINUOUS_DATA.

I'm not familiar with the FIFF file format, so am wondering if anyone knows
whether it is likely the failure to load the data is due to the warnings
given at the Matlab end, or I should be looking elsewhere?

Cheers,
Nick
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