Transpose

class baseband_tasks.shaping.Transpose(ih, sample_axes)

Bases: baseband_tasks.shaping.ChangeSampleShapeBase

Reshapes the axes of the samples of a stream.

Useful to ensure bring, e.g., frequencies and polarizations in groups before dechannelizing.

Parameters

ihtask or baseband stream reader

Input data stream.

sample_axestuple of int

Where the input sample shape axes should end up in the output sample shape (as for transpose). Should contain all axes of the sample shape, starting at 1 (time axis 0 always stays in place).

See also

Reshape

to reshape the samples

ReshapeAndTranspose

to reshape the samples and transpose the axes

GetItem

index or slice the samples

GetSlice

slice the time axis and index or slice the samples

ChangeSampleShape

to change the samples with a user-supplied function.

Examples

The VDIF example file from Baseband has 8 threads which contain 4 channels and 2 polarizations. To produce a stream in which the sample axes are polarization and frequency, one could do:

>>> import numpy as np, astropy.units as u, baseband
>>> from baseband_tasks.shaping import ChangeSampleShape
>>> fh = baseband.open(baseband.data.SAMPLE_VDIF)
>>> fh.frequency = 311.25 * u.MHz + (np.arange(8.) // 2) * 16. * u.MHz
>>> fh.sideband = 1
>>> fh.polarization = np.tile(['L', 'R'], 4)
>>> rh = Reshape(fh, (4, 2))
>>> th = Transpose(rh, (2, 1))
>>> th.read(2).shape
(2, 2, 4)
>>> th.polarization
array([['L'],
       ['R']], dtype='<U1')
>>> th.frequency  
<Quantity [311.25, 327.25, 343.25, 359.25] MHz>
>>> th.sideband
array(1, dtype=int8)
>>> fh.close()

Note that the example above could also be done in one go using ReshapeAndTranspose.

Methods Summary

task(data)

Transpose the axes of data.

Methods Documentation

task(data)

Transpose the axes of data.