# combining planar gradiometers

**URL:** <https://mne.discourse.group/t/combining-planar-gradiometers/1898>\
**Category:** Mailing List Archive (read-only)\
**Tags:** list-archive\
**Created:** [July 18, 2019, 12:54pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898 "2019-07-18T12:54:48Z")\
**Posts on this page:** 6\
**Page:** 1

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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:** [July 18, 2019, 12:54pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898/1 "2019-07-18T12:54:48Z")

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hi,

is there some possibility to combine the respective pairs of planar  
gradiometers (i.e. compute the RMS) and store these in a Evoked object?  
this would be really handy when doing stats or comparing conditions  
otherwise....

best,  
thomas

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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:** [July 18, 2019, 4:32pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898/2 "2019-07-18T16:32:53Z")

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Hi Thomas,

I would use EvokedArray:  
[https://martinos.org/mne/stable/generated/mne.EvokedArray.html](https://martinos.org/mne/stable/generated/mne.EvokedArray.html)

to do the job. You may need to write a few lines of numpy. Let me know if  
you need help with that.

Best,  
Mainak

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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:** [July 18, 2019, 7:06pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898/3 "2019-07-18T19:06:45Z")

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hi mainak,

yes, that would be a kind of hacky way to do it. i was just wondering,  
if a solution similar to the ft\_combineplanar one in fieldtrip existed  
for MNE, including a dedicated sensor type etc...

best,  
thomas

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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:** [July 18, 2019, 7:23pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898/4 "2019-07-18T19:23:55Z")

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hi,

there is everything you need in private methods in the mne/viz module.  
It would need to be exposed in a public function and to be able to return  
for example a fresh evoked object.

would you have time to do a PR thomas,

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:** [July 18, 2019, 7:25pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898/5 "2019-07-18T19:25:58Z")

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All,

Does evoked.as\_type() do something like this? E.g. [https://martinos.org/mne/stable/auto\_examples/preprocessing/plot\_virtual\_evoked.html](https://martinos.org/mne/stable/auto_examples/preprocessing/plot_virtual_evoked.html)

Best,

Jon

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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:** [July 18, 2019, 7:37pm UTC](https://mne.discourse.group/t/combining-planar-gradiometers/1898/6 "2019-07-18T19:37:36Z")

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hi Jon,

no as\_type lets you map between actually sensor types.

Alex