unpack_table

Context: data

Synopsis

Unpack a FITS binary file into a data structure.

Syntax

unpack_table(filename, ncols=2, colkeys=None, dstype=Data1D)

Examples

Example 1

Read in the first two columns of the file, as the independent (X) and dependent (Y) columns of a data set:

>>> d = unpack_table('sources.fits')

Example 2

Read in the first three columns (the third column is taken to be the error on the dependent variable):

>>> d = unpack_table('sources.fits', ncols=3)

Example 3

Read in from columns 'RMID' and 'SUR_BRI':

>>> d = unpack_table('rprof.fits', colkeys=['RMID', 'SUR_BRI'])

Example 4

The first three columns are taken to be the two independent axes of a two-dimensional data set ( x0 and x1 ) and the dependent value ( y ):

>>> d = unpack_table('fields.fits', ncols=3,
...                  dstype=Data2D)

Example 5

When using the Crates I/O library, the file name can include CIAO Data Model syntax, such as column selection. This can also be done using the `colkeys` parameter, as shown above:

>>> d = unpack_table('rprof.fits[cols rmid,sur_bri,sur_bri_err]',
...                  ncols=3)

PARAMETERS

The parameters for this function are:

Parameter	Type information	Definition
filename		Identify the file to read: a file name, or a data structure representing the data to use, as used by the I/O backend in use by Sherpa: a tablecrate for crates, as used by CIAO, or a list of AstroPy HDU objects.
ncols	int, optional	The number of columns to read in (the first `ncols` columns in the file). The meaning of the columns is determined by the `dstype` parameter.
colkeys	array of str, optional	An array of the column name to read in. The default is none .
dstype	optional	The data class to use. The default is `Data1D` and it is expected to be derived from `sherpa.data.BaseData` .

Return value

The return value from this function is:

The class of the returned object is controlled by the `dstype` parameter.

Bugs

See the bugs pages on the Sherpa website for an up-to-date listing of known bugs.