unpack_ascii

sherpa.astro.ui.unpack_ascii(filename, ncols=2, colkeys=None, dstype=<class 'sherpa.data.Data1D'>, sep=' ', comment='#')

Unpack an ASCII file into a data structure.

Parameters:
  • filename (str) – The name of the file to read in. Selection of the relevant column depends on the I/O library in use (Crates or AstroPy).
  • 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.
  • sep (str, optional) – The separator character. The default is ' '.
  • comment (str, optional) – The comment character. The default is '#'.
  • dstype (optional) – The data class to use. The default is Data1D and it is expected to be derived from sherpa.data.BaseData.
Returns:

The type of the returned object is controlled by the dstype parameter.
Return type:

instance

See also

load_ascii()
Load an ASCII file as a data set.
set_data()
Set a data set.
unpack_table()
Unpack a FITS binary file into a data structure.

Examples

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

>>> d = unpack_ascii('sources.dat')

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

>>> d = unpack_ascii('sources.dat', ncols=3)

Read in from columns ‘col2’ and ‘col3’:

>>> d = unpack_ascii('tbl.dat', colkeys=['col2', 'col3'])

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_ascii('fields.dat', ncols=3,
                     dstype=sherpa.astro.data.Data2D)

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_ascii('tbl.dat[cols rmid,sur_bri,sur_bri_err]',
                     ncols=3)