[Mne_analysis] howto convert ICA components to SSP projection operators.

[Alexandre Gramfort]

hi,

it must be one component per projector. Projector data are 1d.

Alex

On Wed, Aug 16, 2017 at 10:19 PM, Luke Bloy <luke.bloy at gmail.com> wrote:
> Thanks Dan and Alex.
>
> How are multiple rows of the projector used? In SSP (PCA) the basis vectors
> are orthogonal however ICA components may not be.
>
> Would you suggest putting all of the excluded ica components into a single
> projector or to build separate projectors for each excluded ICA component?
>
> --Luke
>
> On Wed, Aug 16, 2017 at 1:40 PM Dan McCloy <drmccloy at uw.edu> wrote:
>>
>> Luke,
>> I've created projectors "by hand" like this (caveat: my intent was just to
>> plot topomaps, not to actually apply the projector):
>>
>> desc = '4Hz_artifact_ICA'
>> data = dict(data=my_component, nrow=1, ncol=len(my_component),
>>             row_names=desc, col_names=epochs.ch_names)
>> projector = mne.io.Projection(data=data, active=False, kind=1,
>>                               desc=desc, explained_var=None)
>> epochs.add_proj(projector)
>>
>> I've never used it with ICA (only with DSS) but I think in principle it
>> could work the same way?
>> -- dan
>>
>> Daniel McCloy
>> http://dan.mccloy.info/
>> Postdoctoral Research Associate
>> Institute for Learning and Brain Sciences
>> University of Washington
>>
>>
>> On Wed, Aug 16, 2017 at 9:53 AM, Alexandre Gramfort
>> <alexandre.gramfort at inria.fr> wrote:
>>>
>>> Hi Luke,
>>>
>>> we don't have such a function AFAIK and I see a use to it. My first
>>> reaction was to tall you to use a high n_pca_components in ICA but
>>> it's not fully equivalent to an SSP.
>>>
>>> proj = make_ica_proj(ica, picks)
>>>
>>> ?
>>>
>>> Alex
>>>
>>> On Wed, Aug 16, 2017 at 3:50 PM, Luke Bloy <luke.bloy at gmail.com> wrote:
>>> > Before I potentially reinvent a wheel, I was wondering if there was a
>>> > way to
>>> > compute an ssp projection operator (proj) from the excluded basis set
>>> > of an
>>> > ICA operator.
>>> >
>>> > The reason I'm trying to do this is that I have some data that has an
>>> > environmental artifact that is always around 4HZ but whose topology
>>> > changes
>>> > slightly from subject to subject. ICA on a filtered dataset (3.5-4.5Hz)
>>> > makes it easy to ID the artifact components but the remaining ICA
>>> > components
>>> > are not really applicable to the broadband signal so using ica.apply()
>>> > on
>>> > the boradband signal doesn't really work for me.
>>> >
>>> > Thanks
>>> > Luke
>>> >
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>>
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