[FieldTrip] no 'grad' field after ft_appenddata

Es, M.W.J. van (Mats) M.vanEs at donders.ru.nl
Wed Jul 8 22:16:31 CEST 2015

Hi everyone,

For my experiment I have three MEG sessions. For analysis I preprocessed them and combined them using ft_appenddata. However, the 'grad' field in the data structured is then removed. When I call ft_megplanar (see code)  to do time frequency analysis I get the following error (matlab2013a in cluster, latest fieldtrip version):
cfg                 = [];
cfg.method          = 'template';
cfg.template        = 'CTF275_neighb.mat';
% neighbours          = ft_prepare_neighbours(cfg, alldatacorrect);
neighbours          = ft_prepare_neighbours(cfg, alldata);

cfg                 = [];
cfg.method          = 'sincos';
cfg.neighbours      = neighbours;
% data_planar_correct = ft_megplanar(cfg, alldatacorrect);
data_planar         = ft_megplanar(cfg, alldata);

Error using ft_checkdata (line 527)
This function requires MEG data with a 'grad' field

Error in ft_megplanar (line 96)
data = ft_checkdata(data, 'datatype', {'raw' 'freq'}, 'feedback', 'yes', 'hassampleinfo', 'yes', 'ismeg', 'yes', 'senstype', {'ctf151', 'ctf275', 'bti148',
'bti248', 'itab153', 'yokogawa160', 'yokoga

I already looked at the 'grad' field of the individual sessions and they are not the same. How should I solve this?

Thanks for your help,
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