[FieldTrip] ft_appenddata issue - "cannot append this data"

[Thilan Tudor]

Thank you! Yes, when I run isequal to compare the time of LFP_proc_ftdata
and EEG_proc_ftdata variables it returns logical = 0. After importing the
LFP data, it needs to be resampled to 100 Hz since the EEG data has a
sampling rate of 100Hz.

When I look at the cell array for EEG_proc_ftdata.time, each cell in the
array goes from 0.01 s to 30 s in 0.01 increments, whereas for
LFP_proc_ftdata.time it is from (0.0070 s to 29.997 s in 0.01 increments).
When looking at LFP_data (the LFP data before the 250 Hz to 100 Hz
resampling), LFP_data.time is a cell array 1 x 1332  of 1 x 7500 double as
expected, with time starting at 0.004 and going up in 0.004 increments.

Is there a way to get the time to align between the two so that they are
equivalent (after LFP data is resampled from 250-->100Hz)?

Thanks!

The resampling code is:
cfg = [];
cfg.resamplefs = 100;
LFP = ft_resampledata(cfg, LFP_data.ftdata);

cfg = [];
cfg.refchannel = 'all';
cfg.reref = 'yes';
cfg.refmethod = 'bipolar';
cfg.bpfilter = 'yes';
cfg.bpfreq = [1,49];
LFP_proc_ftdata = ft_preprocessing(cfg,LFP);

On Thu, Mar 23, 2023 at 12:14 AM Schoffelen, J.M. (Jan Mathijs) via
fieldtrip <fieldtrip at science.ru.nl> wrote:

> Hi Thilan,
>
> Have you checked the code? The section in ft_appenddata between line
> 128-136 should give you pointers to what is going on.
>
> My conclusion would be that the condition on line 131 is not met -
> specifically  isequaltime=False - which causes the error.
>
> I need to check the equality of the ’time’ field for the LFP_proc_ftdata
> and EEG_proc_ftdata variables. If this field numerically non-identical, the
> data cannot be appended.
>
> Good luck,
>
> Jan-Mathijs
>
>
> On 22 Mar 2023, at 22:11, Thilan Tudor via fieldtrip <
> fieldtrip at science.ru.nl> wrote:
>
> Hi,
>
> Thanks in advance for the help.
>
> I am trying to use ft_appenddata to merge EEG and iEEG (LFP) data as input
> to run connectivity analysis with ft_connectivity (after processing this
> merged data with ft_freqanalysis).
>
> EEG data has the following channels: 'F3', 'C3', 'A2', 'O1', 'F4', 'A1',
> 'C4', 'O2'
> LFP data has the following channels: 'LFP1-LFP2', 'LFP2-LFP3'
>
> For my same-subject data, I have the following (output from
> ft_preprocessing):
>
> LFP_proc_ftdata =
>
>   struct with fields:
>
>      trialinfo: [1332×1 double]
>        fsample: 100
>     sampleinfo: [1332×2 double]
>          trial: {1×1332 cell}
>           time: {1×1332 cell}
>          label: {2×1 cell}
>            cfg: [1×1 struct]
>
>  EEG_proc_ftdata =
>
>   struct with fields:
>
>      trialinfo: [1332×1 double]
>        fsample: 100
>     sampleinfo: [1332×2 double]
>          trial: {1×1332 cell}
>           time: {1×1332 cell}
>          label: {8×1 cell}
>            cfg: [1×1 struct]
>
>
> I get the following error when I run
>
> cfg = [];
> data_merged = ft_appenddata(cfg, proc_ftdata, LFP_proc_ftdata);
>
> Warning: the data has overlapping segments or originates from different
> recordings on disk
> Warning: please consider specifying cfg.keepsampleinfo='no'
> Error using ft_appenddata
> cannot append this data
>
> Even when I specify cfg.keepsampleinfo='no', I still get "cannot append
> this data". Is the issue is that there are no common channels between the
> datasets to run ft_appenddata?
>
>
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