swh:1:snp:5d08e1a590957faccdc77737b5e8f49534d091bc
Tip revision: c1e89ccdd82e4aade9749fe295647b9771f0c8d2 authored by Bryna Hazelton on 15 February 2017, 23:47:58 UTC
another bug
another bug
Tip revision: c1e89cc
tutorial.rst
Tutorial
========
Example 1
---------
Converting between tested data formats
a) miriad (aipy) -> uvfits
**************************
::
from pyuvdata import UVData
UV = UVData()
miriad_file = 'pyuvdata/data/new.uvA'
UV.read_miriad(miriad_file) # this miriad file is known to be a drift scan
UV.write_uvfits('new.uvfits', force_phase=True, spoof_nonessential=True) # write out the uvfits file
b) uvfits -> miriad (aipy)
**************************
::
from pyuvdata import UVData
UV = UVData()
uvfits_file = 'pyuvdata/data/day2_TDEM0003_10s_norx_1src_1spw.uvfits'
UV.read_uvfits(uvfits_file)
UV.write_uvfits('day2_TDEM0003_10s_norx_1src_1spw.uv') # write out the miriad file
c) FHD -> uvfits
****************
When reading FHD format, we need to point to several files.::
from pyuvdata import UVData
UV = UVData()
fhd_prefix = 'pyuvdata/data/fhd_vis_data/1061316296_'
# Construct the list of files
fhd_files = [fhd_prefix + f for f in ['flags.sav', 'vis_XX.sav', 'params.sav',
'vis_YY.sav', 'vis_model_XX.sav',
'vis_model_YY.sav', 'settings.txt']]
UV.read_fhd(fhd_files)
UV.write_uvfits('1061316296.uvfits', spoof_nonessential=True)
d) FHD -> miriad (aipy)
****************
::
from pyuvdata import UVData
UV = UVData()
fhd_prefix = 'pyuvdata/data/fhd_vis_data/1061316296_'
# Construct the list of files
fhd_files = [fhd_prefix + f for f in ['flags.sav', 'vis_XX.sav', 'params.sav',
'vis_YY.sav', 'vis_model_XX.sav',
'vis_model_YY.sav', 'settings.txt']]
UV.read_fhd(fhd_files)
UV.write_uvfits('1061316296.uvfits')
Example 2
---------
Phasing/unphasing data::
from pyuvdata import UVData
import ephem
UV = UVData()
miriad_file = 'pyuvdata/data/new.uvA'
UV.read_miriad(miriad_file)
print(UV.phase_type) # Data is a drift scan
UV.phase_to_time(UV.time_array[0]) # Phases the data to the zenith at first time step
print(UV.phase_type) # Data should now be phased
UV.unphase_to_drift() # Undo phasing to try another phase center
UV.phase(5.23368, 0.710940, ephem.J2000) # Phase to a specific ra/dec/epoch (in radians)
Example 3
---------
Making a simple waterfall plot::
from pyuvdata import UVData
import numpy as np
import matplotlib.pyplot as plt
UV = UVData()
filename = 'pyuvdata/data/day2_TDEM0003_10s_norx_1src_1spw.uvfits'
UV.read_uvfits(filename)
print(UV.data_array.shape) # Data should have shape (Nblts, Nspws, Nfreqs, Npols)
print(UV.Ntimes) # Number of time samples in data
print(UV.Nfreqs) # Number of frequency channels in data
bl = UV.antnums_to_baseline(1, 2) # Convert antenna numbers (e.g. 1, 2) to baseline number
bl_ind = np.where(UV.baseline_array == bl)[0] # Indices corresponding to baseline
plt.imshow(np.abs(UV.data_array[bl_ind, 0, :, 0])) # Amplitude waterfall for 0th spectral window and 0th polarization
plt.show()