sep.kron_radius¶
-
sep.
kron_radius
(data, x, y, a, b, theta, r, mask=None, maskthresh=0.0)¶ Calculate Kron “radius” within an ellipse.
The Kron radius is given by
\[\sum_i r_i I(r_i) / \sum_i I(r_i)\]where the sum is over all pixels in the aperture and the radius is given in units of
a
andb
:r_i
is the distance to the pixel relative to the distance to the ellipse specified bya
,b
,theta
. Equivalently, after converting the ellipse parameters to their coefficient representation,r_i
is given by\[r_i^2 = cxx(x_i - x)^2 + cyy(y_i - y)^2 + cxx(x_i - x)(y_i - y)\]Parameters: data :
ndarray
Data array.
x, y : array_like
Ellipse center(s).
a, b, theta : array_like
Ellipse parameters.
r : array_like
“Radius” of ellipse over which to integrate. If the ellipse extent correponds to second moments of an object, this is the number of “isophotal radii” in Source Extractor parlance. A Fixed value of 6 is used in Source Extractor.
mask :
numpy.ndarray
, optionalAn optional mask.
maskthresh : float, optional
Pixels with mask > maskthresh will be ignored.
Returns: kronrad : array_like
The Kron radius.
flag : array_like
Integer value indicating conditions about the aperture or how many masked pixels it contains.