analyse_data.py

#!/usr/bin/env python -u

# Find sources in the data and produce spectra for each suitable source.

# Author James Dempsey
# Date 28 Aug 2016

from __future__ import print_function, division

import argparse
import magmo
import sgps
import os
import sys
import time
import csv
from string import Template

from astropy.io import fits
from astropy.io import votable, ascii
from astropy.coordinates import SkyCoord, Angle
from astropy.wcs import WCS
from astropy.table import Table, Column
from astropy.io.votable.tree import Param,Info
from astropy.io.votable import from_table, writeto
from astropy import units as u
import matplotlib.pyplot as plt
import math
import numpy as np
import numpy.core.records as rec
from scipy.signal import savgol_filter



sn_min = 1.3
num_chan = 627


class IslandRange(object):
    def __init__(self, isle_id):
        self.isle_id = isle_id


def parseargs():
    """
    Parse the command line arguments
    :return: An args map with the parsed arguments
    """
    parser = argparse.ArgumentParser(
        description="Find sources in the data for a day and produce spectra for each suitable source.")

    parser.add_argument("filename", help="The name of the file to be analysed.")
    parser.add_argument("-o", "--output_folder", help="The parent folder to write out the spectra.", default='spectra')
    parser.add_argument("--extract_only", help="Use the previous source finding results to extract spectra", default=True,
                        action='store_true')

    args = parser.parse_args()
    return args


def build_output_folder(filename, parent_folder):
    # Expected format is THOR_HI_with_continuum_L15.00_image
    paths = filename.split('/')
    parts = paths[-1].split('_')
    field_name = parts[4]
    output_folder = parent_folder + '/' + field_name
    magmo.ensure_dir_exists(output_folder)
    return output_folder, field_name


def get_high_signal_fields(day_dir_name):
    """
    Retrieve a list of fields observed in a particular day that have sufficient
    signal to noise to search for background sources.
    :param day_dir_name: The name of the day's directory.
    :return: A list of high signal fields.
    """
    field_list = []
    print ("Fields of interest:")
    with open(day_dir_name + '/stats.csv', 'rb') as stats:
        reader = csv.reader(stats)
        first = True
        for row in reader:
            if first:
                first = False
            else:
                if float(row[3]) > sn_min:
                    print (row)
                    field_list.append(row[0])

    return field_list


def find_sources(day_dir_name, field_name):
    """
    Search a continuum file for sources using the Aegean source finder. A
    VOTable file containing the list of discovered sources will be written out
    for the field. This function will use the Aegean source finder
    ( https://github.com/PaulHancock/Aegean ) to identify the sources.

    :param day_dir_name: The name of the day's directory.
    :param field_name:  The name fo the field to be searched for sources.
    :return: A list of error messages, if any
    """
    error_list = []
    cont_file = day_dir_name + "/1757/magmo-" + field_name + "_1757_restor.fits"
    table_file = day_dir_name + "/" + field_name + '_src.vot'
    try:
        print ("##--## Searching continuum image " + cont_file + " ##--##")
        magmo.run_os_cmd('bane ' + cont_file)
        aegean_cmd = 'aegean ' + cont_file + ' --autoload --telescope=ATCA ' \
                     '--cores=1 --island --table=' + table_file
        magmo.run_os_cmd(aegean_cmd)
    except magmo.CommandFailedError as e:
        error_list.append(str(e))
    return error_list


def read_sources(filename):
    print ("Extracting sources from " + filename)
    sources = []

    if not os.path.exists(filename):
        print ("Warning: File %s does not exist, skipping source read." % \
               filename)
        return sources

    results = ascii.read("catalog.dat")
    results['col1'].name = 'id'
    results['col2'].name = 'ra'
    results['col3'].name = 'dec'
    results['col4'].name = 'peak_flux'
    results['col5'].name = 'sn'

    #src_votable = votable.parse(filename, pedantic=False)
    #results = src_votable.get_first_table().array
    for row in results:
        id = row['id']
        ra = row['ra']
        dec = row['dec']
        sn = row['sn']
        flux = row['peak_flux']
        print ("Found source %s at %.4f, %.4f with flux %.4f and sn of %.4f " % (id, ra, dec, flux, sn))
        if sn > 10 and flux > 0.02:
            src = dict(zip(results.dtype.names,row))
            # Create a single pixel size
            src['a'] = 0.00001
            src['b'] = 0.00001
            src['pa'] = 0.0
            #sources.append([ra, dec, id, flux, row['island']])
            sources.append(src)
        else:
            print ("Ignoring source at %.4f, %.4f due to low S/N of %.4f or "
                   "flux of %.4f" % (ra, dec, sn, flux))

    return sources


def read_islands(filename):
    print ("Extracting islands from " + filename)
    islands = {}

    if not os.path.exists(filename):
        print ("Warning: File %s does not exist, skipping island read." % \
               filename)
        return {}

    isle_votable = votable.parse(filename, pedantic=False)
    results = isle_votable.get_first_table().array
    for row in results:
        islands[row['island']] = row
    return islands


def calc_island_ranges(islands, pixel_size):
    island_ranges = []
    for island in islands.values():
        ir = IslandRange(island['island'])
        ra = island['ra']
        dec = island['dec']
        ra_width = abs(island['x_width'] * pixel_size[0])
        dec_width = abs(island['y_width'] * pixel_size[1])
        ir.min_ra = ra - (ra_width/2)
        ir.max_ra = ra + (ra_width/2)
        ir.min_dec = dec - (dec_width/2)
        ir.max_dec = dec + (dec_width/2)
        print("Island %d goes from %f to %f (%d*%f)/ %f to %f (%d*%f)" % (
            island['island'], ir.min_ra, ir.max_ra, island['x_width'], pixel_size[0], ir.min_dec, ir.max_dec,
            island['y_width'], pixel_size[1]))
        island_ranges.append(ir)
    return island_ranges


def read_continuum_ranges():
    continuum_ranges = []
    with open('magmo-continuum.csv', 'rb') as con_def:
        reader = csv.reader(con_def)
        first = True
        for row in reader:
            if first:
                first = False
            else:
                continuum_ranges.append(
                    [int(row[0]), int(row[1]), int(row[2]), int(row[3])])

    print (continuum_ranges)
    return continuum_ranges


def find_edges(fluxes, num_edge_chan):
    """
    Seek from the edges to find where the data starts for this set of fluxes.
    This accounts for an optional number of channels in the data which have no
    data recorded.
    :param fluxes: The array of fluxes to be checked.
    :param num_edge_chan: The number of edge channels with data to be skipped
    :return: The index of the first and last cell to have data.
    """

    l_edge = 0
    r_edge = len(fluxes)-1

    while l_edge < len(fluxes) and fluxes[l_edge] == 0:
        l_edge += 1

    while r_edge > 0 and fluxes[r_edge] == 0:
        r_edge -= 1

    return l_edge + num_edge_chan, r_edge - num_edge_chan


def extract_spectra(fits_filename, continuum_ranges):
    num_edge_chan = 0
    #fits_filename = "{0}/1420/magmo-{1}_1420_sl_restor.fits".format(daydirname,
    #                                                                field)
    src_filename = 'catalog.dat'
    #isle_filename = "{0}/{1}_src_isle.vot".format(daydirname, field)

    spectra = dict()
    source_ids = dict()
    if not os.path.exists(fits_filename):
        print ("Warning: File %s does not exist, skipping extraction." % \
              fits_filename)
        return spectra, source_ids, []

    sources = read_sources(src_filename)
    #islands = read_islands(isle_filename)
    hdulist = fits.open(fits_filename)
    image = hdulist[0].data
    print("Image shape is", image.shape)
    header = hdulist[0].header
    w = WCS(header)
    index = np.arange(header['NAXIS3'])
    beam_maj = header['BMAJ'] * 60 * 60
    beam_min = header['BMIN'] * 60 * 60
    beam_area = math.radians(header['BMAJ']) * math.radians(header['BMIN'])
    print ("Beam was %f x %f arcsec giving area of %f radians^2." % (beam_maj, beam_min, beam_area))
    ranges = [] #calc_island_ranges(islands, (header['CDELT1'], header['CDELT2']))
    velocities = w.wcs_pix2world(10, 10,index[:],0)[2]
    print ("Found {} sources".format(len(sources)))
    for src in sources:
        c = SkyCoord(src['ra'], src['dec'], frame='icrs', unit="deg")

        img_slice = get_integrated_spectrum(image, w, src, c, velocities, c.galactic.l.value, continuum_ranges)
        if img_slice is None:
            continue

        l_edge, r_edge = find_edges(img_slice, num_edge_chan)
        print("Using data range %d - %d out of %d channels." % (
            l_edge, r_edge, len(img_slice)))

        # plotSpectrum(np.arange(slice.size), slice)
        spectrum_array = rec.fromarrays(
            [np.arange(img_slice.size)[l_edge:r_edge],
             velocities[l_edge:r_edge],
             img_slice[l_edge:r_edge]],
            names='plane,velocity,flux')
        spectra[c.galactic.l] = spectrum_array

        # isle = islands.get(src['island'], None)
        src_map = {'id': src['id'], 'flux': src['peak_flux'], 'pos': c, 'beam_area': beam_area}
        src_map['a'] = src['a']
        src_map['b'] = src['b']
        src_map['pa'] = src['pa']
        print (src_map)
        source_ids[c.galactic.l] = src_map
    del image
    del header
    hdulist.close()

    return spectra, source_ids, ranges


def get_weighting_array(data, velocities, longitude, continuum_ranges):
    """
    Calculate the mean of the continuum values. This is based on precalculated regions where there is no gas expected.
    :param data: A cubelet to be analysed, should be a 3D of flux values.
    :param planes: A umpy array of plane, and velocity values.
    :param longitude: The galactic longitude of the target object
    :param continuum_ranges: The predefined continuum blocks by longitude range
    :return: A 2D array of weighting values for the
    """
    continuum_start_vel, continuum_end_vel = magmo.lookup_continuum_range(
        continuum_ranges, int(longitude))

    print(
        "Looking for velocity range %d to %d in data of %d to %d at longitude %.3f" %
        (continuum_start_vel, continuum_end_vel,
         np.min(velocities) / 1000.0,
         np.max(velocities) / 1000.0, longitude))

    continuum_range = np.where(
        continuum_start_vel*1000 < velocities)
    if len(continuum_range) ==0:
        return np.zeros(data.shape[1:2])

    bin_start = continuum_range[0][0]
    continuum_range = np.where(velocities < continuum_end_vel*1000)
    bin_end = continuum_range[0][-1]

    print("Using bins %d to %d (velocity range %d to %d) out of %d" % (
        bin_start, bin_end, continuum_start_vel, continuum_end_vel, len(velocities)))
    print (data.shape)
    continuum_sample = data[bin_start:bin_end, :, :]
    # print ("...gave sample of", continuum_sample)
    mean_cont = np.mean(continuum_sample, axis=0)
    mean_sq = mean_cont ** 2
    sum_sq = np.sum(mean_sq)
    weighting = mean_sq / sum_sq
    print ("Got weighting of {} from {} and {}".format(weighting, mean_sq, sum_sq))
    return weighting


def get_integrated_spectrum(image, w, src, coord, velocities, longitude, continuum_ranges):
    """
    Calculate the integrated spectrum of the component.
    :param image: The image's data array
    :param w: The image's world coordinate system definition
    :param src: The details of the component being processed
    :return: An array of average flux/pixel across the component at each velocity step
    """
    pix = w.wcs_world2pix(coord.galactic.l.value, coord.galactic.b.value, 0, 1)
    if math.isnan(pix[0]):
        print("Source {} at l {} b {} is outside image".format(src['id'], coord.galactic.l.value, coord.galactic.b.value))
        return None

    x_coord = int(round(pix[0])) - 1  # 266
    y_coord = int(round(pix[1])) - 1  # 197
    print("Translated %.4f, %.4f to %d, %d" % (
        src['ra'], src['dec'], x_coord, y_coord))
    radius = 0
    y_min = y_coord - radius
    y_max = y_coord + radius
    x_min = x_coord - radius
    x_max = x_coord + radius
    data = np.copy(image[:, y_min:y_max+1, x_min:x_max+1])
    if data.shape[1] == 0 or data.shape[2] == 0:
        print("Source {} at RA {} Dec {} has no data. Shape was {}".format(src['id'], src['ra'], src['dec'], data.shape))
        return None

    origin = SkyCoord(src['ra'], src['dec'], frame='icrs', unit="deg")
    pa_rad = math.radians(src['pa'])
    total_pixels = (y_max-y_min +1) * (x_max-x_min +1)
    outside_pixels = 0
    for i in range(x_min, x_max+1):
        for j in range(y_min, y_max+1):
            eq_pos = w.wcs_pix2world(i+1, j+1, 0, 1)
            point = SkyCoord(eq_pos[0], eq_pos[1], frame='icrs', unit="deg")
            ##if not point_in_ellipse(origin, point, src['a'], src['b'], pa_rad):
            #    data[:, i-x_min, j-y_min] = 0
            #    outside_pixels += 1
    print("Found {} pixels out of {} inside the component {} at {} {}".format(total_pixels - outside_pixels, total_pixels,
                                                                       src['id'],
                                                                       point.galactic.l.degree,
                                                                       point.galactic.b.degree))
    weighting = get_weighting_array(data, velocities, longitude, continuum_ranges)
    integrated = np.sum(data * weighting, axis=(1, 2))
    inside_pixels = total_pixels - outside_pixels
    if inside_pixels <= 0:
        print ("Error: No data for component!")
    else:
        integrated /= inside_pixels

    return integrated


def get_mean_continuum(spectrum, longitude, continuum_ranges):
    """
    Calculate the mean of the continuum values. This is based on precalculated regions where there is no gas expected.
    :param spectrum: The spectrum to be analysed, should be a numpy array of
        plane, velocity and flux values.
    :param longitude: The galactic longitude of the target object
    :param continuum_ranges: The predefined continuum blocks by longitude range
    :return: A single float which is the mean continuum flux.
    """
    continuum_start_vel, continuum_end_vel = magmo.lookup_continuum_range(
        continuum_ranges, int(longitude))

    print(
        "Looking for velocity range %d to %d in data of %d to %d at longitude %.3f" %
        (continuum_start_vel, continuum_end_vel,
         np.min(spectrum.velocity) / 1000.0,
         np.max(spectrum.velocity) / 1000.0, longitude))

    continuum_range = np.where(
        continuum_start_vel*1000 < spectrum.velocity)
    if len(continuum_range) ==0:
        return None, None, continuum_start_vel, continuum_end_vel

    bin_start = continuum_range[0][0]
    continuum_range = np.where(
        spectrum.velocity < continuum_end_vel*1000)
    bin_end = continuum_range[0][-1]

    print("Using bins %d to %d (velocity range %d to %d) out of %d" % (
        bin_start, bin_end, continuum_start_vel, continuum_end_vel, len(spectrum.velocity)))
    continuum_sample = spectrum.flux[bin_start:bin_end]
    # print ("...gave sample of", continuum_sample)
    mean_cont = np.mean(continuum_sample)
    sd_cont = np.std(continuum_sample/mean_cont)
    return mean_cont, sd_cont, continuum_start_vel, continuum_end_vel


def get_opacity(spectrum, mean):
    """
    Calculate the opacity profile for the spectrum. This simply divides the
    spectrum's flux by the mean.

    :param spectrum: The spectrum to be processed
    :param mean: The mean background flux, representing what the backlighting sources average flux.
    :return: The opacity (e^(-tau)) at each velocity step.
    """
    # print spectrum.flux
    # print spectrum.flux/mean
    return spectrum.flux/mean


def get_temp_bright(spectrum, beam_area, wavelen=0.210996048, ):
    """
    Calculate the brightness temperature (T_B) for the spectrum. This effectively converts the spectrum from units
    of Jy/beam to K.

    :param spectrum: The spectrum to be processed
    :param beam_area: The beam area in radian^2
    :return: The brightness temperature at each velocity step.
    """
    k = 1.3806503E-23  # boltzmann constant in J K^-1
    jy_to_si = 1E-26  # J s^-1 m^-2 Hz^-1

    factor = (wavelen**2 / (2*k)) * jy_to_si / (np.pi*beam_area/4)
    print (factor)
    return factor * spectrum.flux


def name_spectrum(id):
    return id
    #precision = 1000
    #glong = (loc.galactic.l.degree * precision // 1) / precision
    #glat = (loc.galactic.b.degree * precision // 1) / precision
    #return 'MAGMOHI G{:0=7.3f}{:=+06.3f}'.format(glong, glat)


def plot_spectrum(x, y, filename, title, con_start_vel, con_end_vel, sigma_tau):
    """
    Output a plot of opacity vs LSR velocity to a specified file.

    :param x: The velocity data
    :param y: The opacity values for each velocity step
    :param filename: The file the plot should be written to. Should be
         an .eps or .pdf file.
    :param title: The title for the plot
    :param con_start_vel: The minimum velocity that the continuum was measured at.
    :param con_end_vel: The maximum velocity that the continuum was measured at.
    """
    fig = plt.figure()
    plt.plot(x/1000, y)

    if len(sigma_tau) > 0:
        tau_max = 1 + sigma_tau
        tau_min = 1 - sigma_tau
        plt.fill_between(x/1000, tau_min, tau_max, facecolor='lightgray', color='lightgray')

    plt.axhline(1, color='r')
    plt.axvline(con_start_vel, color='g', linestyle='dashed')
    plt.axvline(con_end_vel, color='g', linestyle='dashed')

    plt.xlabel(r'Velocity relative to LSR (km/s)')
    plt.ylabel(r'$e^{(-\tau)}$')
    plt.title(title)
    plt.grid(True)
    plt.savefig(filename)
    #plt.show()
    plt.close()
    return


def plot_emission_spectrum(velocity, em_mean, em_std, filename, title, con_start_vel, con_end_vel):
    """
    Output a plot of emission vs LSR velocity to a specified file.

    :param velocity: The velocity data
    :param em_mean: The mean temperature values for each velocity step
    :param em_std: The standard deviation in temperature values for each velocity step
    :param filename: The file the plot should be written to. Should be
         an .eps or .pdf file.
    :param title: The title for the plot
    :param con_start_vel: The minimum velocity that the continuum was measured at.
    :param con_end_vel: The maximum velocity that the continuum was measured at.
    """

    if len(em_mean) == 0:
        if os.path.exists(filename):
            os.remove(filename)
        return

    fig = plt.figure()
    plt.plot(velocity/1000, em_mean)

    em_max = em_mean + em_std
    em_min = em_mean - em_std
    plt.fill_between(velocity/1000, em_min, em_max, facecolor='lightgray', color='lightgray')

    plt.axvline(con_start_vel, color='g', linestyle='dashed')
    plt.axvline(con_end_vel, color='g', linestyle='dashed')

    plt.xlabel(r'Velocity relative to LSR (km/s)')
    plt.ylabel(r'$T_B$ (K)')
    plt.title(title)
    plt.grid(True)
    plt.savefig(filename)
    #plt.show()
    plt.close()
    return


def output_spectra(spectrum, opacity, filename, longitude, latitude, em_mean, em_std, temp_bright, beam_area,
                   sigma_tau, src_id):
    """
    Write the spectrum (velocity, flux and opacity) to a votable format file.

    :param spectrum: The spectrum to be output.
    :param opacity:  The opacity to be output.
    :param filename:  The filename to be created
    :param longitude: The galactic longitude of the target object
    :param latitude: The galactic latitude of the target object
    """
    table = Table(meta={'name': filename, 'id': 'opacity'})
    table.add_column(Column(name='plane', data=spectrum.plane))
    table.add_column(Column(name='velocity', data=spectrum.velocity, unit='m/s'))
    table.add_column(Column(name='opacity', data=opacity))
    table.add_column(Column(name='flux', data=spectrum.flux, unit='Jy', description='Flux per beam'))
    table.add_column(Column(name='temp_brightness', data=temp_bright, unit='K'))
    table.add_column(Column(name='sigma_tau', data=sigma_tau, description='Noise in the absorption profile'))
    if len(em_mean) > 0:
        # The emission may not be available, so don't include it if not
        table.add_column(Column(name='em_mean', data=em_mean, unit='K'))
        table.add_column(Column(name='em_std', data=em_std, unit='K'))

    votable = from_table(table)
    votable.infos.append(Info('longitude', 'longitude', longitude.value))
    votable.infos.append(Info('latitude', 'latitude', latitude.value))
    votable.infos.append(Info('beam_area', 'beam_area', beam_area))
    votable.infos.append(Info('src_gname', 'gname', src_id))
    writeto(votable, filename)


def output_emission_spectra(filename, longitude, latitude, velocity, em_mean,
                            em_std, ems):
    """
    Write the emission spectrum (velocity, flux and opacity) to a votable format
    file.

    :param filename:  The filename to be created
    :param longitude: The galactic longitude of the target object
    :param latitude: The galactic latitude of the target object
    :param velocity:
    :param em_mean:
    :param em_std:
    :param ems:
    """
    table = Table(meta={'name': filename, 'id': 'emission'})
    table.add_column(Column(name='velocity', data=velocity, unit='m/s'))
    table.add_column(Column(name='em_mean', data=em_mean, unit='K'))
    table.add_column(Column(name='em_std', data=em_std, unit='K'))
    for i in range(len(ems)):
        table.add_column(Column(name='em_'+str(i), data=ems[i].flux, unit='K'))

    votable = from_table(table)
    votable.infos.append(Info('longitude', 'longitude', longitude.value))
    votable.infos.append(Info('latitude', 'latitude', latitude.value))
    writeto(votable, filename)


def point_in_ellipse(origin, point, a, b, pa_rad):
    # Convert point to be in plane of the ellipse
    p_ra_dist = point.icrs.ra.degree - origin.icrs.ra.degree
    p_dec_dist = point.icrs.dec.degree - origin.icrs.dec.degree
    x = p_ra_dist * math.cos(pa_rad) + p_dec_dist * math.sin(pa_rad)
    y = - p_ra_dist * math.sin(pa_rad) + p_dec_dist * math.cos(pa_rad)

    a_deg = a / 3600
    b_deg = a / 3600

    # Calc distance from origin relative to a/b
    dist = math.sqrt((x / a_deg) ** 2 + (y / b_deg) ** 2)
    # print("Point %s is %f from ellipse %f, %f, %f at %s." % (point, dist, a, b, math.degrees(pa_rad), origin))
    return dist <= 1.0


def point_in_island(point, islands):
    ra = point.icrs.ra.degree
    dec = point.icrs.dec.degree
    for island in islands:
        if island.min_ra <= ra <= island.max_ra and island.min_dec <= dec <= island.max_dec:
            print("  Point %s in island %d at %f, %f" % (point, island.isle_id, island.min_ra, island.min_dec))
            return True
    # print("Point %f, %f not in any of %d islands" % (ra, dec, len(islands)))
    return False


def emission_has_absorption(coord, emission):
    #ems = sgps.extract_spectra([coord, ], file_list)
    if emission:
        spectrum = emission.flux
        if np.min(spectrum) > -12:
            return False
        else:
            print("  coord l {:.4f} b {:.4f} has absorption {:.2f}".format(coord.galactic.l.value,
                                                                           coord.galactic.b.value, np.min(spectrum)))

    return True


def cache_sgps_spectra(sample_points, file_list):
    coords = np.array(sample_points)
    orig_shape = coords.shape
    coords = coords.flatten()
    spectra = sgps.extract_spectra(coords, file_list)
    sample_spectra = np.array(spectra).reshape(orig_shape)
    return sample_spectra


def calc_all_points(origin, num_points, beam_size, max_dist, step_fraction=0.5):
    spacing = 2.0 * math.pi / float(num_points)
    step_size = beam_size * step_fraction
    num_steps = int(max_dist / step_size)
    coord_list = []
    print ("Steps", num_steps, step_size)
    for i in range(0, num_points):
        angle = spacing * i
        vector = []
        for step in range(1, num_steps+1):
            distance = step * step_size
            g_l = origin.galactic.l.value + math.sin(angle)*distance
            g_b = origin.galactic.b.value + math.cos(angle)*distance
            coord = SkyCoord(g_l, g_b, frame='galactic', unit="deg")
            vector.append(coord)
        coord_list.append(vector)
    print ("First coord", coord_list[0][0])
    return coord_list


def calc_offset_points(longitude, latitude, beam_size, a, b, pa, islands, file_list, num_points=6, max_dist=0.3611):
    # spacing = 2.0 * math.pi / float(num_points)
    origin = SkyCoord(longitude, latitude, frame='galactic', unit="deg")
    coord = origin
    pa_rad = math.radians(pa)
    sample_points = calc_all_points(origin, num_points, beam_size, max_dist)
    sample_emisison_spectra = cache_sgps_spectra(sample_points, file_list)
    points = []
    for i in range(0, num_points):
        for step in range(len(sample_points[i])):
            coord = sample_points[i][step]
            inside_component = point_in_ellipse(origin, coord, a, b, pa_rad) or point_in_island(coord, islands)
            if inside_component:
                coord = None
                continue
            emission = sample_emisison_spectra[i][step]
            if not emission_has_absorption(coord, emission):
                break

            # Not found yet
            coord = None

        if coord is None:
            print("Point could not be found for angle %d within max dist of %f (max steps %d)" % (
                i, max_dist, len(sample_points[i])))
        else:
            print("Point at angle %d is at l %.4f b %.4f with mult %d" % (
                i, coord.galactic.l.value, coord.galactic.b.value, step))
            points.append(coord)

    return points


def get_emission_spectra(centre, velocities, file_list, filename_prefix, a, b, pa, islands):
    """
    Extract SGPS emission spectra around a central point.

    :param centre: A SkyCoord containing the location of the central point
    :param velocities: The velocities list sothat the emission data can be matched.
    :param file_list: A list of dictionaries describing the SGPS files.
    :paeram a: semi-major axis length in arcsec of the component ellipse
    :paeram b: semi-minor axis length in arcsec of the component ellipse
    :paeram pa: parallactic angle of the component ellipse
    :return: An array fo the mean and standard deviation of emission at each velocity.
    """

    #file_list = sgps.get_hi_file_list()
    filename = filename_prefix + '_emission.votable.xml'
    coords = calc_offset_points(centre.galactic.l.value,
                                centre.galactic.b.value, 0.03611, a, b, pa, islands, file_list)
    ems = sgps.extract_spectra(coords, file_list)
    print("Found {} emission points from {} coords for point l={}, b={}".format(len(ems), len(coords),
                                                                                centre.galactic.l.value,
                                                                                centre.galactic.b.value))
    if ems:
        all_em = np.array([ems[i].flux for i in range(len(ems))])
        em_std = np.std(all_em, axis=0)
        em_mean = np.mean(all_em, axis=0)
        em_std_interp = np.interp(velocities, ems[0].velocity, em_std)
        em_mean_interp = np.interp(velocities, ems[0].velocity, em_mean)
        em_mean_interp = savgol_filter(em_mean_interp, 9, 2)

        output_emission_spectra(filename,
                                centre.galactic.l, centre.galactic.b,
                                ems[0].velocity, em_mean, em_std, ems)

        return em_mean_interp, em_std_interp

    print("WARNING: Unable to find emission data for " + str(centre))
    if os.path.exists(filename):
        os.remove(filename)
    return [], []


def calc_sigma_tau(cont_sd, em_mean, opacity):
    """
    Calculate the noise in the absorption profile at each velocity step. Where emission data is available, this is
    based on the increased antenna temperature due to the received emission.

    :param cont_sd: The measured noise in the continuum region of the spectrum in absorption units.
    :param em_mean: The mean emission brightness temperature in K
    :param opacity: The optical depth spectrum, used only for the shape of the data
    :return: A numpy array containing the noise level in the optical depth data at each velocity step.
    """
    tsys = 44.7
    if len(em_mean) > 0:
        floor = np.zeros(em_mean.shape)
        sigma_tau = cont_sd * ((tsys + np.fmax(floor, em_mean)) / tsys)
    else:
        sigma_tau = np.full(opacity.shape, cont_sd)
    return sigma_tau


def produce_spectra(filename, continuum_ranges, field, day=None, dirname='spectra'):
    file_list = sgps.get_hi_file_list()
    magmo.ensure_dir_exists(dirname)
    with open(dirname + '/spectra.html', 'w') as spectra_idx:
        t = Template(
            '<html>\n<head><title>D$day Spectra</title></head>\n'
            + '<body>\n<h1>Spectra previews for day $day</h1>\n<table>\n')
        spectra_idx.write(t.substitute(day=day))

        neg_mean = 0
        no_mean = 0
        all_cont_sd = []
        all_opacity = []
        spectra, source_ids, islands = extract_spectra(filename, continuum_ranges)
        t = Template('<tr><td colspan=4><b>Field: ${field}</b></td></tr>\n' +
                     '<tr><td>Image Name</td><td>Details</td>' +
                     '<td>Absorption</td><td>Emission</td></tr>\n')
        spectra_idx.write(t.substitute(field=field))

        idx = 0
        for longitude in sorted(spectra.keys()):
            spectrum = spectra.get(longitude)
            src_data = source_ids.get(longitude)
            name_prefix = field + '_src' + src_data['id']
            idx += 1
            mean, cont_sd, min_con_vel, max_con_vel = get_mean_continuum(
                spectrum,
                longitude.degree,
                continuum_ranges)
            if mean is None:
                print("WARNING: Skipped spectrum %s with no continuum data" % (name_prefix, mean))
                no_mean += 1
                continue

            if mean < 0:
                print(("WARNING: Skipped spectrum %s with negative " +
                      "mean: %.5f") % (name_prefix, mean))
                neg_mean += 1
                continue

            spectrum_name = name_spectrum(src_data['id'])
            print('Continuum mean of %s (%s) is %.5f Jy, sd %.5f' % (
                spectrum_name, name_prefix, mean, cont_sd))
            all_cont_sd.append(cont_sd)
            opacity = get_opacity(spectrum, mean)
            temp_bright = get_temp_bright(spectrum, src_data['beam_area'])
            dir_prefix = dirname +  "/"

            em_mean, em_std = [], []  #get_emission_spectra(src_data['pos'],
                                   #                spectrum.velocity,
                                   #                file_list, dir_prefix + name_prefix,
                                   #                src_data['a'], src_data['b'], src_data['pa'], islands)
            # print opacity
            sigma_tau = calc_sigma_tau(cont_sd, em_mean, opacity)
            img_name = name_prefix + "_plot.png"
            plot_spectrum(spectrum.velocity, opacity, dir_prefix + img_name,
                          "Spectra for source {}".format(
                              spectrum_name), min_con_vel, max_con_vel, sigma_tau)
            filename = dir_prefix + name_prefix + '_opacity.votable.xml'
            latitude = src_data['pos'].galactic.b

            em_img_name = name_prefix + "_emission.png"
            plot_emission_spectrum(spectrum.velocity, em_mean, em_std,
                                   dir_prefix + name_prefix + "_emission.png",
                                   "Emission around {0}".format(
                                       spectrum_name), min_con_vel,
                                   max_con_vel)
            output_spectra(spectrum, opacity, filename, longitude, latitude,
                           em_mean, em_std, temp_bright, src_data['beam_area'], sigma_tau, src_data['id'])
            all_opacity.append(opacity)

            t = Template('<tr><td>${img}</td><td>${name}<br/>l:&nbsp;${longitude}<br/>' +
                         'Peak:&nbsp;${peak_flux}&nbsp;Jy<br/>Mean:&nbsp;${mean}&nbsp;Jy<br/>'
                         'Cont&nbsp;SD:&nbsp;${cont_sd}</td><td><a href="${img}">' +
                         '<img src="${img}" width="500px"></a></td><td><a href="${em_img}">' +
                         '<img src="${em_img}" width="500px"></a></td></tr>\n')
            spectra_idx.write(t.substitute(img=img_name, em_img=em_img_name, peak_flux=src_data['flux'],
                                           longitude=longitude, mean=mean, cont_sd=cont_sd, name=spectrum_name))


        spectra_idx.write('</table></body></html>\n')

        if no_mean > 0:
            print("Skipped %d spectra with no continuum data." % no_mean)

        print("Skipped %d spectra with negative mean continuum." % neg_mean)
        print("Produced %d spectra with continuum sd of %.5f." % (
            len(all_cont_sd), np.mean(all_cont_sd)))
        return all_opacity


def main():
    """
    Main script for analyse_data
    :return: The exit code
    """
    # Read day parameter
    args = parseargs()
    filename = args.filename
    output_folder, field_name = build_output_folder(filename, args.output_folder)
    start = time.time()

    # Check metadata against file system
    #day_dir_name = "day" + day
    if not os.path.isfile(filename):
        print ("File %s could not be found." % filename)
        return 1

    print ("#### Started analysis on file %s at %s ####" % \
          (filename, time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(start))))
    print('# Writing output to', output_folder)
    error_list = []

    # Read list of fields, filter for ones to be processed
    #field_list = get_high_signal_fields(day_dir_name)

    # For each file, find the sources
    #if not args.extract_only:
    #    for field in field_list:
    #        error_list.extend(find_sources(day_dir_name, field))

    # For each file, extract spectra
    continuum_ranges = magmo.get_continuum_ranges()
    produce_spectra(filename, continuum_ranges, field_name, dirname=output_folder)

    # Report
    end = time.time()
    print ('#### Processing completed at %s ####' \
          % (time.strftime('%Y-%m-%d %H:%M:%S', time.localtime(end))))
    print ('Searched images in %.02f s' % (end - start))
    if len(error_list) == 0:
        print ("Hooray! No errors found.")
    else:
        print ("%d errors were encountered:" % (len(error_list)))
        for err in error_list:
            print (err)
    return 0


# Run the script if it is called from the command line
if __name__ == "__main__":
    exit(main())