[FieldTrip] Warning: copying input chantype to Montage in runica

[Felicitas Huber]

Hello community,

I am currently examining peak alpha frequency. To do so, I am analyzing EEG
data collected during a period of 6 minutes of rest.

Prior to running frequency analysis, I am using PCA to remove non-brain
artifacts. While the algorithm seems to work, I am getting the following
warning:

“*Warning: copying input chantype to montage.”*

The script still runs, but I wanted to make sure I understand what
fieldtrip is doing. I am importing the data from eeglab. Below my code:

        cfg = [];
        cfg.dataset = 'epoched_closed.set'; %this is the dataset
        ft_data1 = ft_preprocessing(cfg);
        cfg.length=5;
        cfg.overlap=0;
        data=ft_redefinetrial(cfg,ft_data1);
        cfg.method       = 'runica';
        cfg.runica.pca=15;
       * X=ft_componentanalysis(cfg,data); *%%this is the line that gives
me the warning

The cfg and data I use are as follows:

cfg =
    dataset: 'epoched_closed.set'
     length: 5
    overlap: 0
     method: 'runica'
     runica: [1×1 struct]

data =
         label: {31×1 cell}
       fsample: 500
          elec: [1×1 struct]
           cfg: [1×1 struct]
           hdr: [1×1 struct]
         trial: {1×36 cell}
          time: {1×36 cell}
    sampleinfo: [36×2 double]

I have looked into the warning and am assuming "chantype" lets fieldtrip
know that it is handling eeg data, but would appreciate some more insight
into what fieldtrip is doing behind the scenes (i.e., why the warning pops
up).

Thank you,
Felicitas
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