Matcher (class)

class Matcher(ra, dec, depth=16, log=False, convertToArray=True)

Bases: HMpTy.htm._htmcCode.Matcher

A matcher-array object to match other arrays of ra,dec against

The Matcher object is initialized with a set of ra,dec coordinates and can then be used and reused to match against other sets of coordinates

Key Arguments

• log – logger

• depth – the depth of the mesh generate the Matcher object at. Default 16

• ra – list, numpy array or single ra value

• dec – –list, numpy array or single dec value (must match ra array length)

• convertToArray – convert the coordinates into an array. Default True. Can bypass the conversion check if you are sure coordinates in numpy array

Return

• None

Usage

If we have a set of coordinates such that:

raList1 = [200.0, 200.0, 200.0, 175.23, 21.36]
decList1 = [24.3,  24.3,  24.3,  -28.25, -15.32]

We can initialise a matcher object like so:

from HMpTy import Matcher
coordinateSet = Matcher(
    log=log,
    ra=raList1,
    dec=decList1,
    depth=16
)

Methods

get_depth()
match(ra, dec, radius[, maxmatch])	match a corrdinate set against this Matcher object’s coordinate set

Properties

depth

the depth of the Matcher object

match(ra, dec, radius, maxmatch=1)

match a corrdinate set against this Matcher object’s coordinate set

Key Arguments

• ra – list, numpy array or single ra value

• dec – –list, numpy array or single dec value (must match ra array length)

• radius – radius of circle in degrees

• maxmatch – maximum number of matches to return. Set to 0 to match all points. Default 1 (i.e. closest match)

Return

• None

Usage

Once we have initialised a Matcher coordinateSet object we can match other coordinate sets against it:

twoArcsec = 2.0 / 3600.
raList2 = [200.0, 200.0, 200.0, 175.23, 55.25]
decList2 = [24.3 + 0.75 * twoArcsec, 24.3 + 0.25 * twoArcsec,
    24.3 - 0.33 * twoArcsec, -28.25 + 0.58 * twoArcsec, 75.22]

matchIndices1, matchIndices2, seps = coordinateSet.match(
    ra=raList2,
    dec=decList2,
    radius=twoArcsec,
    maxmatch=0
)

for m1, m2, s in zip(matchIndices1, matchIndices2, seps):
    print(raList1[m1], decList1[m1], " -> ", s * 3600., " arcsec -> ", raList2[m2], decList2[m2])

Or to return just the nearest matches:

matchIndices1, matchIndices2, seps = coordinateSet.match(
    ra=raList2,
    dec=decList2,
    radius=twoArcsec,
    maxmatch=1
)

Note from the print statement, you can index the arrays raList1, decList1 with the matchIndices1 array values and raList2, decList2 with the matchIndices2 values.

property depth

the depth of the Matcher object

Usage

coordinateSet.depth