[FieldTrip] Appending data.grad, after using D.ftraw(0)
George Wallis
wallisgj at gmail.com
Mon Sep 10 14:22:20 CEST 2012
Dear fieldtrippers,
if anyone can help me with this I'd be very grateful!
I have a bunch of preprocessed and epoched data files in SPM format, and
I'm converting them to fieldtrip format using the following:
D = spm_eeg_load(fn);
data = D.ftraw(0);
...which results in...
data =
fsample: 250
label: {350x1 cell}
trial: {1x360 cell}
time: {1x360 cell}
Comparing this to data structures generated using fieldtrip alone, field
like data.grad are missing.
I can create something like a grad field by doing:
D.sensors('MEG')
ans =
pnt: [510x3 double]
ori: [510x3 double]
tra: [306x510 double]
unit: 'mm'
label: {306x1 cell}
If I then append this to the data:
data.grad = D.sensors('MEG');
I get an error:
---
Error using ft_chantype (line 56)
the input that was provided to this function cannot be deciphered
Error in ft_datatype_sens (line 128)
sens.chantype = ft_chantype(sens);
Error in ft_datatype_raw (line 99)
data.grad = ft_datatype_sens(data.grad);
Error in ft_checkdata (line 177)
data = ft_datatype_raw(data, 'hassampleinfo', hassampleinfo);
Error in ft_timelockanalysis (line 134)
data = ft_checkdata(data, 'datatype', {'raw', 'comp'}, 'feedback', 'yes',
'hassampleinfo',
'yes');
Error in ft_SENS_ERF_grRep (line 82)
avdat = ft_timelockanalysis(cfg,raw);
---
...when I try to do timelockanalysis on this data. If I leave the grad
field off (i.e. not append it to the output of ftraw(0)) there's no
problem, and the analysis runs fine. However, because I want to do spatial
neighbour cluster analysis later, I think I need the .grad field, so I
might as well get it incorporated at this stage.
Going a bit further into the error messages above, the function
ft_datatype_sens appears to convert the old format .ori, .pnt into the
newer .coilori, .coilpos ... etc. But the next function in the chain,
ft_chantype, looks for .pnt and .ori when doing:
isgrad = isa(input, 'struct') && isfield(input, 'pnt') && isfield(input,
'ori');
I'm wondering if this could be the problem?
Sorry for the long message! I'd be very grateful if anyone can help out.
Best wishes,
George
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