imaginglss.model.brickindex module

Python code to provide a high level table/list/index of bricks, and methods for organizing and querying them and returning brick objects.

class imaginglss.model.brickindex.BrickIndex(brickdata)

Bases: object

BrickIndex manages a high level table/list/index of bricks.

It contains methods for organizing and querying bricks or returning brick objects.

The FITS file ‘bricks.fits’ within each imaging data release contains meta-data about each of the bricks in the release.

We generate an index from bricks.fits , e.g.

>>> brickdata = fits.read_table('bricks.fits')
>>> bi = BrickIndex(brickdata) 

However, a BrickIndex object is usually automatically handled by DataRelease, and one shall use

>>> dr = DataRelease()
>>> dr.brickindex

Notes

The bricks in DECALS are first divided as uniform DEC rows. The number of bricks changes with DEC, such that each brick as apporximately same area.

build(NROWS, NCOLS)

get_brick(index)

Obtain a single brick from index.

The returned Brick object is immutable; there is only a single instance per BrickIndex.

Parameters:

index : integer

The internal index of a brick. This differ from BRICKID in the catalogue.

Returns:

brick : Brick

A brick object at index.

Notes

The lack of a vector version is on purpose to emphasize we are dealing with objects.

Use get_bricks() to create a list of objects.

get_bricks(indices)

Obtain a list of bricks.

Parameters:

indices : array_like

Indices to obtain bricks

Returns:

bricks : list

A list of bricks.

init_from_state()

optimize(coord, return_index=False, return_inverse=False)

Optimize the ordering of coord=(RA,DEC) to make later queries faster.

RA and DEC are sorted by their brickid, to group future queries.

Parameters:

return_inverse : boolean

if True, returns the array that can be used to reconstruct coord from the returned coord.

return_index : boolean

if True, returns the array that can be used to construct sorted_coord from coord:

Returns:

Depending or return_inverse and return_index, may return

(sorted_coord, indices, iindices), (sorted_coord, iindices)

(sorted_coord, indices), or sorted_coord

sorted_coord : array_like

Optimized coord array, that is sorted by bricks.

iindeces : array_like

sorted_ra[ iindices] == ra sorted_dec[iindices] == dec

indices : array_like

sorted_ra == ra[indices] sorted_dec == dec[indices]

query(coord)

Returns a brick at coord=(RA,DEC) in decimal degrees.

Parameters:

coord : array_like

coord = (RA, DEC) in degrees, vectorized.

query_internal(coord)

Returns the internal index of a brick at coord=(RA,DEC) in decimal degrees.

Parameters:

coord : array_like

coord = (RA, DEC) in degrees, vectorized.

Notes

Get Brick objects with get_bricks() or get_brick().

query_region(extent)

Returns a list of bricks covering the extent in decimal degrees.

Parameters:

extent : tuple, list

extent = (RA1, RA2, DEC1, DEC2) in degrees.

Notes

RA1 is the left side and RA2 is the right side.

search_by_id(brickid)

Search the brickindex for bricks with a given brickid.

Parameters:

brickid : integer or array_like

the matching BRICKID or list of BRICKIDs

Returns:

index : integer or array_like

the internal index of brick or bricks (for array_like input)

Notes

Get Brick objects with get_bricks() or get_brick().

search_by_name(brickname)

Search the brickindex for bricks with a given name.

Parameters:

brickname : string

the matching BRICKNAME.

Returns:

index : integer

The internal index of bricks.

Notes

This function is not vectorized.