orca.transform.dftspectrum
==========================

.. py:module:: orca.transform.dftspectrum

.. autoapi-nested-parse::

   Direct Fourier Transform spectrum extraction.

   Provides functions for phase-shifting visibility data to extract spectra
   at arbitrary sky positions using DFT techniques. This allows extracting
   spectra for sources that are not at the phase center.

   Functions
   ---------
   phase_shift_vis
       Phase shift visibility data to a new sky position.
   dftspectrum
       Compute DFT spectrum at specified positions (not yet implemented).
   phase_data_to_pos_inplace
       In-place phase shift of visibility data array.

   .. admonition:: Notes

      INVERSE_C_MS is 1/c in units of seconds per meter (3.3356e-9 s/m).



Attributes
----------

.. autoapisummary::

   orca.transform.dftspectrum.INVERSE_C_MS


Functions
---------

.. autoapisummary::

   orca.transform.dftspectrum.phase_shift_vis
   orca.transform.dftspectrum.dftspectrum
   orca.transform.dftspectrum.phase_data_to_pos_inplace


Module Contents
---------------

.. py:data:: INVERSE_C_MS
   :value: 3.3356409519815204e-09


.. py:function:: phase_shift_vis(t: casacore.tables.table, freqs: numpy.ndarray, phase_center: astropy.coordinates.SkyCoord, pos: astropy.coordinates.SkyCoord, columnname: str, startrow: int = 0, nrow: int = -1, rowincr: int = 1) -> numpy.ndarray

   Phase shift visibility data column and return the shifted data. It does not write back to the table, nor does it
   shift the UVW coordinates. Only works with data with one spectral window.

   :param t: table containing the data
   :param freqs: (1, N_chan) channel array. Can get from tspw.getcol('CHAN_FREQ').
   :param phase_center: current phase center.
   :param pos: position to shift to.
   :param columnname: column name for the data.
   :param startrow: see casacore getcol documentation.
   :param nrow: see casacore getcol documentation.
   :param rowincr: see casacore getcol documentation.

   Returns: the phased shifted data



.. py:function:: dftspectrum(data: numpy.ndarray, uvw: numpy.ndarray, freqs: numpy.ndarray, ra0_rad: float, dec0_rad: float, ra_rad: numpy.ndarray, dec_rad: numpy.ndarray, weights: Optional[numpy.ndarray] = None)

.. py:function:: phase_data_to_pos_inplace(data: numpy.ndarray, uvw: numpy.ndarray, freqs: numpy.ndarray, ra0_rad: float, dec0_rad: float, ra_rad: float, dec_rad: float)