astro py:docs

- Index
- Modules

### Navigation

- next »
- « previous |
- Astropy v5.2.1 »
- Astrostatistics Tools (`astropy.stats`) »
- bayesian_blocks

# bayesian_blocks

astropy.stats.bayesian_blocks(t, x=None, sigma=None, fitness='events', **kwargs)

  Compute optimal segmentation of data with Scargle’s Bayesian Blocks

  This is a flexible implementation of the Bayesian Blocks algorithm described in Scargle 2013 [1].

  Parameters:
    t numpy:array_like

      data times (one dimensional, length N)

    x numpy:array_like, optional

      data values

    sigma numpy:array_like or `python:float`, optional

      data errors

    fitness `python:str` or `object`

      the fitness function to use for the model. If a string, the following options are supported:

      - ‘events’ : binned or unbinned event data. Arguments are `gamma`, which gives the slope of the prior on the number of bins, or `ncp_prior`, which is \(-\ln({\tt gamma})\).

      - ‘regular_events’ : non-overlapping events measured at multiples of a fundamental tick rate, `dt`, which must be specified as an additional argument. Extra arguments are `p0`, which gives the false alarm probability to compute the prior, or `gamma`, which gives the slope of the prior on the number of bins, or `ncp_prior`, which is \(-\ln({\tt gamma})\).

      - ‘measures’ : fitness for a measured sequence with Gaussian errors. Extra arguments are `p0`, which gives the false alarm probability to compute the prior, or `gamma`, which gives the slope of the prior on the number of bins, or `ncp_prior`, which is \(-\ln({\tt gamma})\).

      In all three cases, if more than one of `p0`, `gamma`, and `ncp_prior` is chosen, `ncp_prior` takes precedence over `gamma` which takes precedence over `p0`.

      Alternatively, the fitness parameter can be an instance of `FitnessFunc` or a subclass thereof.

    **kwargs

      any additional keyword arguments will be passed to the specified `FitnessFunc` derived class.

  Returns:
    edges `ndarray`

      array containing the (N+1) edges defining the N bins

  See also

  `astropy.stats.histogram`

    compute a histogram using bayesian blocks

  References

  [1]

  Scargle, J et al. (2013) https://ui.adsabs.harvard.edu/abs/2013ApJ…764..167S

  [2]

  Bellman, R.E., Dreyfus, S.E., 1962. Applied Dynamic Programming. Princeton University Press, Princeton. https://press.princeton.edu/books/hardcover/9780691651873/applied-dynamic-programming

  [3]

  Bellman, R., Roth, R., 1969. Curve fitting by segmented straight lines. J. Amer. Statist. Assoc. 64, 1079–1084. https://www.tandfonline.com/doi/abs/10.1080/01621459.1969.10501038

  Examples

  Event data:

      >>> t = np.random.normal(size=100)
      >>> edges = bayesian_blocks(t, fitness='events', p0=0.01)

  Event data with repeats:

      >>> t = np.random.normal(size=100)
      >>> t[80:] = t[:20]
      >>> edges = bayesian_blocks(t, fitness='events', p0=0.01)

  Regular event data:

      >>> dt = 0.05
      >>> t = dt * np.arange(1000)
      >>> x = np.zeros(len(t))
      >>> x[np.random.randint(0, len(t), len(t) // 10)] = 1
      >>> edges = bayesian_blocks(t, x, fitness='regular_events', dt=dt)

  Measured point data with errors:

      >>> t = 100 * np.random.random(100)
      >>> x = np.exp(-0.5 * (t - 50) ** 2)
      >>> sigma = 0.1
      >>> x_obs = np.random.normal(x, sigma)
      >>> edges = bayesian_blocks(t, x_obs, sigma, fitness='measures')