match_coordinates_3d¶
-
astropy.coordinates.
match_coordinates_3d
(matchcoord, catalogcoord, nthneighbor=1, storekdtree=u'_kdtree_3d')[source] [edit on github]¶ Finds the nearest 3-dimensional matches of a coordinate or coordinates in a set of catalog coordinates.
This finds the 3-dimensional closest neighbor, which is only different from the on-sky distance if
distance
is set in eithermatchcoord
orcatalogcoord
.Parameters: matchcoord :
BaseCoordinateFrame
orSkyCoord
The coordinate(s) to match to the catalog.
catalogcoord :
BaseCoordinateFrame
orSkyCoord
The base catalog in which to search for matches. Typically this will be a coordinate object that is an array (i.e.,
catalogcoord.isscalar == False
)nthneighbor : int, optional
Which closest neighbor to search for. Typically
1
is desired here, as that is correct for matching one set of coordinates to another. The next likely use case is2
, for matching a coordinate catalog against itself (1
is inappropriate because each point will find itself as the closest match).storekdtree : bool or str, optional
If a string, will store the KD-Tree used for the computation in the
catalogcoord
, as an attribute incatalogcoord
with the provided name. This dramatically speeds up subsequent calls with the same catalog. If False, the KD-Tree is discarded after use.Returns: idx : integer array
Indices into
catalogcoord
to get the matched points for eachmatchcoord
. Shape matchesmatchcoord
.sep2d :
Angle
The on-sky separation between the closest match for each
matchcoord
and thematchcoord
. Shape matchesmatchcoord
.dist3d :
Quantity
The 3D distance between the closest match for each
matchcoord
and thematchcoord
. Shape matchesmatchcoord
.Notes
This function requires SciPy to be installed or it will fail.