# Matrix mapping sensor to source

**URL:** <https://mne.discourse.group/t/matrix-mapping-sensor-to-source/1523>\
**Category:** Mailing List Archive (read-only)\
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**Created:** [May 15, 2018, 2:47pm UTC](https://mne.discourse.group/t/matrix-mapping-sensor-to-source/1523 "2018-05-15T14:47:35Z")\
**Posts on this page:** 3\
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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [May 15, 2018, 2:47pm UTC](https://mne.discourse.group/t/matrix-mapping-sensor-to-source/1523/1 "2018-05-15T14:47:35Z")

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Hi!

Is it possible to retrieve the matrix performing the mapping of sensor to  
source space for MEG data? That is not a function but an object that can  
be treated as a matrix?

Best,  
Karin  
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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [May 15, 2018, 6:28pm UTC](https://mne.discourse.group/t/matrix-mapping-sensor-to-source/1523/2 "2018-05-15T18:28:14Z")

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hi,

look at matrix K as used here:

[https://github.com/mne-tools/mne-python/blob/master/mne/minimum\_norm/inverse.py#L930](https://github.com/mne-tools/mne-python/blob/master/mne/minimum_norm/inverse.py#L930)

HTH  
Alex

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**Author:** ![system](https://global.discourse-cdn.com/free1/uploads/mne/original/1X/85cc6bd2b69cb698a166dc6d880fb550510d0144.jpeg) [@system](https://mne.discourse.group/u/system)\
**Post date:** [May 16, 2018, 3:05pm UTC](https://mne.discourse.group/t/matrix-mapping-sensor-to-source/1523/3 "2018-05-16T15:05:43Z")

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Thanks!  
I have continuous meg data from epilepsy patients and I would like to filter my data so that my output will be one continuous time series representing (as good as possible) the activity stemming only from the epileptic focus. Would it be possible to achieve this creating a spatial filter by multiplying K with a vector of dimension (306x1) with time point with maximum spike amplitude and then multiplying this ?filter? with the raw data (resulting in one row vector reflecting activity in the source of spiking activity)?

Karin