# Y axis limits in PPSD plots

**URL:** https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885
**Category:** Users Mailing List Archive
**Tags:** archive
**Created:** [April 24, 2020, 5:02pm UTC](https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885 "2020-04-24T17:02:49Z")
**Posts on this page:** 5
**Page:** 1

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### Author: ![Robert\_Sohn](https://discourse.obspy.org/letter_avatar_proxy/v4/letter/r/a9a28c/32.png) [@Robert\_Sohn](https://discourse.obspy.org/u/Robert_Sohn)
#### Post date: [April 24, 2020, 5:02pm UTC](https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885/1 "2020-04-24T17:02:49Z")

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How can I change the default y-axis limits in PPSD.plot?

Thanks, Rob

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### Author: ![megies](https://discourse.obspy.org/user_avatar/discourse.obspy.org/megies/32/9_2.png) [@megies](https://discourse.obspy.org/u/megies)
#### Post date: [April 27, 2020, 9:08am UTC](https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885/2 "2020-04-27T09:08:12Z")

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Use show=False, don't use filename=... and then work with the returned  
matplotlib Figure object and call pyplot show when done or save to file.

Something like  
fig = ppsd.plot(...)  
fig.axes[0].set\_ylim(..., ...)

cheers,  
Tobias

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### Author: ![Robert\_Sohn](https://discourse.obspy.org/letter_avatar_proxy/v4/letter/r/a9a28c/32.png) [@Robert\_Sohn](https://discourse.obspy.org/u/Robert_Sohn)
#### Post date: [April 27, 2020, 1:54pm UTC](https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885/3 "2020-04-27T13:54:23Z")

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Thanks for the help. It's not quite working, though...

I use the following code:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fig = ppsd.plot(show=False,xaxis\_frequency=True,period\_lim=(0.002, 10),cmap=pqlx,show\_noise\_models=False)  
&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;fig.axes[0].set\_ylim(-140, -20)

And get, for example, the attached figure. Although I can change the upper y-axis limit to -20, the plot doesn't show anything above -50, which is the upper y-axis limit in the default settings, even though there is signal up there. Note that I am plotting hydrophone data, which is why the dB levels are not aligned with 'normal' seismometer data.

Does this have something to do with db\_bin\_edges setting in the ppsd routine?

Thanks, Rob

Quoting Tobias Megies \<megies@geophysik.uni-muenchen.de\>:

 ![PPSD_A00_05.2020.png](https://discourse.obspy.org/uploads/default/original/1X/58d70bab7d671cdd71a1519a5793c2e3ef30ebf0.png)

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### Author: ![megies](https://discourse.obspy.org/user_avatar/discourse.obspy.org/megies/32/9_2.png) [@megies](https://discourse.obspy.org/u/megies)
#### Post date: [April 29, 2020, 8:26am UTC](https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885/4 "2020-04-29T08:26:00Z")

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So you do not want the plot limits to change, but the processing  
parameters. You need to specify that when initializing your PPSD before  
feeding in data:

[http://docs.obspy.org/master/packages/autogen/obspy.signal.spectral\_estimation.PPSD.\_\_init\_\_.html?highlight=db\_bins](http://docs.obspy.org/master/packages/autogen/obspy.signal.spectral_estimation.PPSD. __init__.html?highlight=db_bins)

ppsd = PPSD(..., db\_bins=...)

best,  
Tobias

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<div class="post-metadata">

### Author: ![Robert\_Sohn](https://discourse.obspy.org/letter_avatar_proxy/v4/letter/r/a9a28c/32.png) [@Robert\_Sohn](https://discourse.obspy.org/u/Robert_Sohn)
#### Post date: [April 29, 2020, 11:54am UTC](https://discourse.obspy.org/t/y-axis-limits-in-ppsd-plots/885/5 "2020-04-29T11:54:45Z")

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Thanks. I now see it has to be done by setting the db\_bins parameter.

Best, Rob

Quoting Tobias Megies \<megies@geophysik.uni-muenchen.de\>: