# Help with Data Challenge 3

**URL:** <https://ask.igwn.org/t/help-with-data-challenge-3/349>\
**Category:** Open Data Workshop\
**Created:** [June 1, 2022, 2:48pm UTC](https://ask.igwn.org/t/help-with-data-challenge-3/349 "2022-06-01T14:48:13Z")\
**Posts on this page:** 5\
**Page:** 1

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**Author:** ![npurnima](https://avatars.discourse-cdn.com/v4/letter/n/eada6e/32.png) [@npurnima](https://ask.igwn.org/u/npurnima)\
**Post date:** [June 1, 2022, 2:48pm UTC](https://ask.igwn.org/t/help-with-data-challenge-3/349/1 "2022-06-01T14:48:13Z")

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I am using the tool `q_transform ` from pycbc to transforms the time series signal into a frequency-time plot and I am stuck with the following -

1. how does changing q values affect the plot or what is the significance of the range of q values? (I tried various q ranges to be able to see the signal in the plot below but I was unable to spot it)
2. I do not understand how to read the x-axis with the UTC time. For example, in the following plot, if I want to narrow my window to 5.6s - 6.4s, how do I format the outseg argument?  
 ![image (3)](https://canada1.discourse-cdn.com/flex031/uploads/gwosc/original/1X/d171855821e8d2924d80c831f3e8e0258931a9ce.png)

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**Author:** ![jonah](https://yyz1.discourse-cdn.com/flex031/user_avatar/ask.igwn.org/jonah/32/10_2.png) [@jonah](https://ask.igwn.org/u/jonah)\
**Post date:** [June 1, 2022, 8:31pm UTC](https://ask.igwn.org/t/help-with-data-challenge-3/349/2 "2022-06-01T20:31:40Z")

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Hi! Thank you for your question!

Are you using the `q_transform` from pycbc or gwpy?

1. The q-value should correspond to the number of cycles in the LIGO band. You can see some notes in the following places:

[quickview app](https://share.streamlit.io/jkanner/streamlit-dataview/app.py) - Click “see notes” under the q-transform plot.

[intro tutorials](https://github.com/jkanner/gw-intro/blob/main/extra/Estimate%20Q-value.ipynb)

1. For pycbc, you could try something like the code below.  
For `gwpy`, you might look instead at the [Quickview notebook](https://mybinder.org/v2/gh/losc-tutorial/quickview/master?filepath=index.ipynb)

```auto
t0 = 1204
data = pycbc_strain.time_slice(t0-10, t0+10)
times, freqs, power = data.qtransform(.001, logfsteps=100,
                                                qrange=(3, 10),
                                                frange=(10, 1024)
                                         )
plt.figure(figsize=[15, 3])
plt.pcolormesh(times, freqs, power**0.5)
plt.xlim(t0-2, t0+2)
plt.ylim(10,1024)
plt.yscale('log')
plt.clim(0,20)
plt.colorbar()
plt.show()

```

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<div class="post-metadata">

**Author:** ![npurnima](https://avatars.discourse-cdn.com/v4/letter/n/eada6e/32.png) [@npurnima](https://ask.igwn.org/u/npurnima)\
**Post date:** [June 2, 2022, 4:14am UTC](https://ask.igwn.org/t/help-with-data-challenge-3/349/3 "2022-06-02T04:14:51Z")

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Hi Jonah,  
I am using q\_transform from gwpy (apologies for the incorrect statement earlier). Thank you for the resources, they were helpful.

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**Author:** ![Arunan23](https://avatars.discourse-cdn.com/v4/letter/a/da6949/32.png) [@Arunan23](https://ask.igwn.org/u/Arunan23)\
**Post date:** [May 30, 2023, 8:48am UTC](https://ask.igwn.org/t/help-with-data-challenge-3/349/4 "2023-05-30T08:48:21Z")

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Hello, for q-transform in challenge I am getting this. Quit a long glitch?

 ![image](https://canada1.discourse-cdn.com/flex031/uploads/gwosc/original/1X/4b8ed091ecd76bbbba78618427a11d8c6208ab05.jpeg)

For this data set, how to find starting time for bilby analysis?

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**Author:** ![jonah](https://yyz1.discourse-cdn.com/flex031/user_avatar/ask.igwn.org/jonah/32/10_2.png) [@jonah](https://ask.igwn.org/u/jonah)\
**Post date:** [May 30, 2023, 4:06pm UTC](https://ask.igwn.org/t/help-with-data-challenge-3/349/5 "2023-05-30T16:06:00Z")

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@Arunan23 Thank you for your questions!

Yes - that looks like a glitch! Probably [scattering arches, as described in this paper](https://arxiv.org/abs/2007.14876)

For bilby, you want to give bilby a few seconds of data, with the merger time in the center. So - maybe a 4 or 16 second window, with the merger time in the center.