# Error with Baseline

**URL:** <https://mne.discourse.group/t/error-with-baseline/3503>\
**Category:** Support & Discussions\
**Tags:** preprocessing, eeg, statistics, visualization\
**Created:** [August 7, 2021, 10:22am UTC](https://mne.discourse.group/t/error-with-baseline/3503 "2021-08-07T10:22:36Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Res](https://avatars.discourse-cdn.com/v4/letter/r/ba9def/32.png) [@Res](https://mne.discourse.group/u/Res)\
**Post date:** [August 7, 2021, 10:22am UTC](https://mne.discourse.group/t/error-with-baseline/3503/1 "2021-08-07T10:22:36Z")

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I am trying to baseline my data using:

power=tfr\_array\_morlet(epochs.get\_data(), sfreq=epochs.info[‘sfreq’], freqs=freqs, n\_cycles=n\_cycles, output=‘avg\_power’)

rescale(power, epochs.times, (-0.2, 0.2), mode=‘zscore’)

But I obtain an output with only NaN values (while using ‘mean’ it works fine). How can I manage to get a result with ‘zscore’?

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**Author:** ![agramfort](https://avatars.discourse-cdn.com/v4/letter/a/7c8e57/32.png) [@agramfort](https://mne.discourse.group/u/agramfort)\
**Post date:** [August 7, 2021, 12:33pm UTC](https://mne.discourse.group/t/error-with-baseline/3503/2 "2021-08-07T12:33:35Z")

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I suspect the standard deviation of your power during baseline is zero so the zscore is NaN

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<div class="post-metadata">

**Author:** ![Res](https://avatars.discourse-cdn.com/v4/letter/r/ba9def/32.png) [@Res](https://mne.discourse.group/u/Res)\
**Post date:** [August 7, 2021, 12:50pm UTC](https://mne.discourse.group/t/error-with-baseline/3503/3 "2021-08-07T12:50:54Z")

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Thanks! Should I then try some data transformation? (if yes, do you have any suggestions?) Or does this mean that I can’t apply ‘zscore’ in this case?

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**Author:** ![agramfort](https://avatars.discourse-cdn.com/v4/letter/a/7c8e57/32.png) [@agramfort](https://mne.discourse.group/u/agramfort)\
**Post date:** [August 7, 2021, 1:25pm UTC](https://mne.discourse.group/t/error-with-baseline/3503/4 "2021-08-07T13:25:07Z")

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I suspect your baseline is too short