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

[Luke Bloy]

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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