# Amplitude of interpolated channels very small

**URL:** <https://mne.discourse.group/t/amplitude-of-interpolated-channels-very-small/1511>\
**Category:** Mailing List Archive (read-only)\
**Tags:** list-archive\
**Created:** [May 8, 2018, 7:21am UTC](https://mne.discourse.group/t/amplitude-of-interpolated-channels-very-small/1511 "2018-05-08T07:21:54Z")\
**Posts on this page:** 4\
**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:** [May 8, 2018, 7:21am UTC](https://mne.discourse.group/t/amplitude-of-interpolated-channels-very-small/1511/1 "2018-05-08T07:21:54Z")

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Hello everyone,

most of the time interpolate\_bads() works well but I have some data sets  
where the amplitude of the interpolated channels is significantly  
smaller than the amplitudes of the surrounding channels.

In the following Dropbox link are two examples of data sets before  
interpolation and after interpolation (marked with 'bcc' in the  
filename). Channels 7, 10, 142, and 156 are dead in the original data  
sets. After interpolation, the channels still appear to be dead/ flat  
when plotting the data, however, looking at the raw data for these  
channels we can see that the values are now different from zero. Redoing  
the interpolation yields the same result.

[https://www.dropbox.com/sh/11rjc45bbg2b38m/AACUW6rtZKcJKitEMfbMIKVqa?dl=0](https://www.dropbox.com/sh/11rjc45bbg2b38m/AACUW6rtZKcJKitEMfbMIKVqa?dl=0)

Why does the interpolation work for some data sets and not for others?

Best,

Christian Kiefer

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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 8, 2018, 1:09pm UTC](https://mne.discourse.group/t/amplitude-of-interpolated-channels-very-small/1511/2 "2018-05-08T13:09:14Z")

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Hi,

Can you also share a script to demonstrate the problem?

Thanks

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:** [May 8, 2018, 2:29pm UTC](https://mne.discourse.group/t/amplitude-of-interpolated-channels-very-small/1511/3 "2018-05-08T14:29:42Z")

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Hi,

I used visual inspection to mark the bad channels. Basically it came  
down to:

# load raw data  
import mne  
raw\_fname = '/path/to/file'  
raw = mne.io.Raw(raw\_fname, preload=True)  
# mark bads  
raw.plot(block=True)  
raw.interpolate\_bads(reset\_bads=True)

Hope that helps!

Christian

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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 13, 2018, 9:54am UTC](https://mne.discourse.group/t/amplitude-of-interpolated-channels-very-small/1511/4 "2018-05-13T09:54:55Z")

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External Email - Use Caution

hi Christian,

can you open an issue here:

[https://github.com/mne-tools/mne-python/issues](https://github.com/mne-tools/mne-python/issues)

so we can follow up on this?

provide as much details as possible (code snippet, figure, data)

thanks  
Alex