This documentation is for astroML version 0.2

This page

Links

astroML Mailing List

GitHub Issue Tracker

Videos

Scipy 2012 (15 minute talk)

Scipy 2013 (20 minute talk)

Citing

If you use the software, please consider citing astroML.

11.4.5. astroML.datasets.fetch_dr7_quasar

astroML.datasets.fetch_dr7_quasar(data_home=None, download_if_missing=True)

Loader for SDSS DR7 quasar catalog

Parameters :

data_home : optional, default=None

Specify another download and cache folder for the datasets. By default all scikit learn data is stored in ‘~/astroML_data’ subfolders.

download_if_missing : optional, default=True

If False, raise a IOError if the data is not locally available instead of trying to download the data from the source site.

Returns :

data : ndarray, shape = (105783,)

numpy record array containing the quasar catalog

Notes

Not all available data is extracted and saved. The extracted columns are:

sdssID, RA, DEC, redshift, mag_u, err_u, mag_g, err_g, mag_r, err_r, mag_i, err_i, mag_z, err_z, mag_J, err_J, mag_H, err_H, mag_K, err_K, specobjid

many of the objects are missing 2mass photometry.

More information at http://www.sdss.org/dr7/products/value_added/qsocat_dr7.html

Examples

>>> from astroML.datasets import fetch_dr7_quasar
>>> data = fetch_dr7_quasar()
>>> u_g = data['mag_u'] - data['mag_g']
>>> u_g[:3]  # first three u-g colors
array([-0.07699966,  0.03600121,  0.10900116], dtype=float32)