SkyStats

class stcal.skymatch.skystatistics.SkyStats(skystat='mean', lower=None, upper=None, nclip=5, lsig=4.0, usig=4.0, binwidth=0.1)[source]

Bases: object

Class built on top of stsci.imagestats.ImageStats.

Deligates its functionality to calls to the ImageStats object. Compared to stsci.imagestats.ImageStats, SkyStats has “persistent settings” in the sense that object’s parameters need to be set once and these settings will be applied to all subsequent computations on different data.

Initialize the SkyStats object.

Parameters:

  • skystat (optional) – possible values are ‘mean’, ‘median’, ‘mode’, ‘midpt”. Sets the statistics that will be returned by ~stcal.skymatch.skystatistics.SkyStats.calc_sky. The following statistics are supported: ‘mean’, ‘mode’, ‘midpt’, and ‘median’. First three statistics have the same meaning as in stsdas.toolbox.imgtools.gstatistics while ‘median’ will compute the median of the distribution.

  • lower (float, None, optional) – Lower limit of usable pixel values for computing the sky. This value should be specified in the units of the input image(s).

  • upper (float, None, optional) – Upper limit of usable pixel values for computing the sky. This value should be specified in the units of the input image(s).

  • nclip (int, optional) – A non-negative number of clipping iterations to use when computing the sky value.

  • lsig (float, optional) – Lower clipping limit, in sigma, used when computing the sky value.

  • usig (float, optional) – Upper clipping limit, in sigma, used when computing the sky value.

  • binwidth (float, optional) – Bin width, in sigma, used to sample the distribution of pixel brightness values in order to compute the sky background statistics.

Methods Summary

__call__(data)

Call self as a function.

calc_sky(data)

Compute statistics on data.

Methods Documentation

__call__(data)[source]

Call self as a function.

calc_sky(data)[source]

Compute statistics on data.

Parameters:

data (numpy.ndarray) – A numpy array of values for which the statistics needs to be computed.

Returns:

statistics – A tuple of two values: (skyvalue, npix), where skyvalue is the statistics specified by the skystat parameter during the initialization of the SkyStats object and npix is the number of pixels used in computing the statistics reported in skyvalue.

Return type:

tuple