# How window window size is inferred?
**URL:** https://mne.discourse.group/t/how-window-window-size-is-inferred/1843
**Category:** Mailing List Archive (read-only)
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**Created:** [May 12, 2019, 2:47pm UTC](https://mne.discourse.group/t/how-window-window-size-is-inferred/1843 "2019-05-12T14:47:26Z")
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### Author:  [@system](https://mne.discourse.group/u/system)
#### Post date: [May 12, 2019, 2:47pm UTC](https://mne.discourse.group/t/how-window-window-size-is-inferred/1843/1 "2019-05-12T14:47:26Z")
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Dear MNE-community,
In example "Decoding in time-frequency space data using the Common Spatial
Pattern (CSP)" (
[https://mne-tools.github.io/dev/auto\_examples/decoding/plot\_decoding\_csp\_timefreq.html#sphx-glr-auto-examples-decoding-plot-decoding-csp-timefreq-py](https://mne-tools.github.io/dev/auto_examples/decoding/plot_decoding_csp_timefreq.html#sphx-glr-auto-examples-decoding-plot-decoding-csp-timefreq-py)),
I did not understand the concept behind inferring window size based on
frequency being used(line 81-82). Can you please explain shortly why and
how window size is inferred?
Regards
Manoj
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### Author:  [@system](https://mne.discourse.group/u/system)
#### Post date: [May 12, 2019, 7:08pm UTC](https://mne.discourse.group/t/how-window-window-size-is-inferred/1843/2 "2019-05-12T19:08:40Z")
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I guess you refer to these lines:
# Infer window size based on the frequency being used
w\_size = n\_cycles / ((fmax + fmin) / 2.) # in seconds
the size of the filter applied depends on the filtering. For low frequencies
you need longer filters. I guess this is a way to inject this idea
when cropping time windows.
Hope this helps
Alex