biweight_location¶
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astropy.stats.
biweight_location
(a, c=6.0, M=None)[source] [edit on github]¶ Compute the biweight location for an array.
Returns the biweight location for the array elements. The biweight is a robust statistic for determining the central location of a distribution.
The biweight location is given by the following equation
\[\begin{split}C_{bl}= M+\frac{\Sigma_{\|u_i\|<1} (x_i-M)(1-u_i^2)^2} {\Sigma_{\|u_i\|<1} (1-u_i^2)^2}\end{split}\]where M is the sample mean or if run iterative the initial guess, and u_i is given by
\[u_{i} = \frac{(x_i-M)}{cMAD}\]where MAD is the median absolute deviation.
For more details, see Beers, Flynn, and Gebhardt, 1990, AJ, 100, 32B
Parameters: a : array-like
Input array or object that can be converted to an array.
c : float
Tuning constant for the biweight estimator. Default value is 6.0.
M : float, optional
Initial guess for the biweight location.
Returns: biweight_location : float
Returns the biweight location for the array elements.
Examples
This will generate random variates from a Gaussian distribution and return the biweight location of the distribution:
>>> from astropy.stats.funcs import biweight_location >>> from numpy.random import randn >>> randvar = randn(10000) >>> cbl = biweight_location(randvar)