uniform_sample¶

sherpa.astro.ui.uniform_sample(num=1, factor=4, id=None, otherids=(), numcores=None)

Sample the fit statistic by taking the parameter values from an uniform distribution.

For each iteration (sample), change the thawed parameters by drawing values from a uniform distribution, and calculate the fit statistic.

Parameters
• num (int, optional) – The number of samples to use (default is 1).

• factor (number, optional) – Multiplier to expand the scale parameter (default is 4).

• id (int or str, optional) – The data set that provides the data. If not given then all data sets with an associated model are used simultaneously.

• otherids (sequence of int or str, optional) – Other data sets to use in the calculation.

• numcores (optional) – The number of CPU cores to use. The default is to use all the cores on the machine.

Returns

A NumPy array table with the first column representing the statistic and later columns the parameters used.

Return type

samples

fit()

Fit a model to one or more data sets.

normal_sample()

Sample from a normal distribution.

set_model()

Set the source model expression for a data set.

set_stat()

Set the statistical method.

t_sample()

Sample from the Student’s t-distribution.

Examples

The model fit to the default data set has three free parameters. The median value of the statistic calculated by uniform_sample is returned:

>>> ans = uniform_sample(num=10000)
>>> ans.shape
(1000, 4)
>>> np.median(ans[:,0])
284.66534775948134