query

Catalog.query(expr: str) → Catalog

Filters catalog and respective margin, if it exists, using a complex query expression

Parameters:

exprstr

Query expression to evaluate. The column names that are not valid Python variables names should be wrapped in backticks, and any variable values can be injected using f-strings. The use of ‘@’ to reference variables is not supported. More information about pandas query strings is available here.

Returns:

Catalog

A catalog that contains the data from the original catalog that complies with the query expression. If a margin exists, it is filtered according to the same query expression.

Examples

Filter a small synthetic catalog using a pandas-style query string:

>>> import lsdb
>>> from lsdb.nested.datasets import generate_data
>>> nf = generate_data(1000, 5, seed=0, ra_range=(0.0, 300.0), dec_range=(-50.0, 50.0))
>>> catalog = lsdb.from_dataframe(nf.compute()[["ra", "dec", "id"]])
>>> filtered = catalog.query("ra < 100 and dec > 0")
>>> filtered.head()
                        ra        dec    id
_healpix_29
118362963675428450  52.696686  39.675892  8154
98504457942331510   89.913567  46.147079  3437
70433374600953220   40.528952  35.350965  8214
154968715224527848   17.57041    29.8936  9853
67780378363846894    45.08384   31.95611  8297