skystatistics¶
The skystatistics
module contains various statistical
functions used by skymatch.
The skystatistics
module provides statistics computation class used by
match()
and SkyImage
.
- class romancal.skymatch.skystatistics.SkyStats(skystat='mean', lower=None, upper=None, nclip=5, lsig=4.0, usig=4.0, binwidth=0.1, **kwargs)[source]¶
This is a superclass build on top of
stsci.imagestats.ImageStats
. Compared tostsci.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.Initializes the SkyStats object.
- Parameters:
skystat ({'mode', 'median', 'mode', 'midpt'}, optional) – Sets the statistics that will be returned by
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.
kwargs (dict) – A dictionary of optional arguments to be passed to
ImageStats
.
- calc_sky(data)[source]¶
Computes 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
), whereskyvalue
is the statistics specified by theskystat
parameter during the initialization of theSkyStats
object andnpix
is the number of pixels used in computing the statistics reported inskyvalue
.- Return type:
tuple