# obspy.core.trace.Trace.decimate

`Trace.``decimate`(factor, no_filter=False, strict_length=False)

  Downsample trace data by an integer factor.

  Parameters: | factor (int) Factor by which the sampling rate is lowered by decimation. no_filter (bool, optional) Deactivates automatic filtering if set to `True`. Defaults to `False`. strict_length (bool, optional) Leave traces unchanged for which end time of trace would change. Defaults to `False`.

  Currently a simple integer decimation is implemented. Only every `decimation_factor`-th sample remains in the trace, all other samples are thrown away. Prior to decimation a lowpass filter is applied to ensure no aliasing artifacts are introduced. The automatic filtering can be deactivated with `no_filter=True`.

  If the length of the data array modulo `decimation_factor` is not zero then the end time of the trace is changing on sub-sample scale. To abort downsampling in case of changing end times set `strict_length=True`.

  Note

  The `Trace` object has three different methods to change the sampling rate of its data: `resample()`, `decimate()`, and `interpolate()`

  Make sure to choose the most appropriate one for the problem at hand.

  Note

  This operation is performed in place on the actual data arrays. The raw data is not accessible anymore afterwards. To keep your original data, use `copy()` to create a copy of your trace object. This also makes an entry with information on the applied processing in `stats.processing` of this trace.

  Example

  For the example we switch off the automatic pre-filtering so that the effect of the downsampling routine becomes clearer:

      >>> tr = Trace(data=np.arange(10))
      >>> tr.stats.sampling_rate
      1.0
      >>> tr.data
      array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])
      >>> tr.decimate(4, strict_length=False,
      ...    no_filter=True)
      <...Trace object at 0x...>
      >>> tr.stats.sampling_rate
      0.25
      >>> tr.data
      array([0, 4, 8])

### Thank you!

We would like to thank our contributors, whose efforts make this software what it is. These people have helped by writing code and documentation, and by testing. They have created and maintained this product, its associated libraries and applications, our build tools and our web sites.

#### Contributors

- Ackerley, Nick
- Allgeyer, Sebastien
- Ammon, Charles J.
- Antunes, Emanuel
- Arnarsson, Ólafur St.
- Bank, Markus
- Barsch, Robert
- Behr, Yannik
- Bernardi, Fabrizio
- Bernauer, Felix
- Bes de Berc, Maxime
- Beyreuther, Moritz
- Boltz, Shawn
- Bonaimé, Sébastien
- Carothers, Lloyd
- Chamberlain, Calum
- Chambers, Derrick
- Chen, Zhao
- Clark, Adam
- Danecek, Peter
- Egdorf, Sven
- Engels, Fabian
- Ermert, Laura
- Eulenfeld, Tom

- Fabbri, Tommaso
- Falco, Nicholas
- Fee, Jeremy
- Grellier, Clément
- Grunberg, Marc
- Hammer, Conny
- Heimann, Sebastian
- Heiniger, Lukas
- Hope, Gaute
- Igel, Heiner
- Inza, Adolfo
- Isken, Marius
- Ketchum, David
- Koymans, Mathijs
- Kremers, Simon
- Kress, Victor
- Krieger, Lars
- Krischer, Lion
- Kula, Damian
- Käufl, Paul
- Köhler, Andreas
- Lecocq, Thomas
- Leeman, John
- Legovini, Paride

- Lesage, Philippe
- Li, Yulin
- Lomax, Anthony
- Lopes, Rui L.
- MacCarthy, Jonathan
- Maggi, Alessia
- Martin, Henri
- Medlin, Andrew
- Megies, Tobias
- Meschede, Matthias
- Michelini, Alberto
- Miller, Nathaniel C.
- Morgenstern, Bernhard
- Nof, Ran Novitsky
- Panning, Mark P.
- Parker, Tom
- Pestourie, Romain
- Rapagnani, Giovanni
- Reyes, Celso
- Ringler, Adam
- Rothenhäusler, Nicolas
- Russo, Emiliano
- Sales de Andrade, Elliott

- Satriano, Claudio
- Saul, Joachim
- Scheingraber, Chris
- Schneider, Simon
- Sippl, Christian
- Snoke, Arthur
- Stange, Stefan
- Stähler, Simon C.
- Sullivan, Benjamin
- Tian, Dongdong
- Trabant, Chad
- Trani, Luca
- Uieda, Leonardo
- Walker, Andrew
- Walther, Marcus
- Wassermann, Joachim
- Williams, Mark C.
- Winkelman, Andrew
- Zaccarelli, Riccardo
- Zad, Seyed Kasra Hosseini
- Zhu, Lijun
- van Driel, Martin
- van Wijk, Kasper

#### Funds

ObsPy was partially funded by the

- German Science Foundation (DFG) via grant DFG IG 16/9-1
- German Ministry for Education and Research (BMBF), GEOTECHNOLOGIEN grant 03G0646H.
- NERA project (Network of European Research Infrastructures for Earthquake Risk Assessment and Mitigation) under the European Community's Seventh Framework Programme (FP7/2007-2013) grant agreement n° 262330
- Leibniz Institute for Applied Geophysics (LIAG)
- VERCE EU-FP7 project (no. 283543)