1 | import _asap
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2 |
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3 | class linefinder:
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4 | """
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5 | The class for automated spectral line search in ASAP.
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6 | """
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7 |
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8 | def __init__(self):
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9 | """
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10 | Create a line finder object.
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11 | """
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12 | self.finder = _asap.linefinder()
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13 | return
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14 |
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15 | def set_options(self,threshold=1.7320508075688772,min_nchan=3,
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16 | avg_limit=8,box_size=0.2):
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17 | """
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18 | Set the parameters of the algorithm
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19 | Parameters:
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20 | threshold a single channel S/N ratio above which the
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21 | channel is considered to be a detection
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22 | Default is sqrt(3), which together with
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23 | min_nchan=3 gives a 3-sigma criterion
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24 | min_nchan a minimal number of consequtive channels,
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25 | which should satisfy a threshold criterion to
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26 | be a detection. Default is 3.
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27 | avg_limit A number of consequtive channels not greater than
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28 | this parameter can be averaged to search for
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29 | broad lines. Default is 8.
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30 | box_size A running mean box size specified as a fraction
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31 | of the total spectrum length. Default is 1/5
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32 | Note: For bad baselines threshold should be increased,
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33 | and avg_limit decreased (or even switched off completely by
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34 | setting this parameter to 1) to avoid detecting baseline
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35 | undulations instead of real lines.
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36 | """
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37 | self.finder.setoptions(threshold,min_nchan,avg_limit,box_size)
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38 | return
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39 |
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40 | def set_scan(self,scan,mask=None,edge=(0,0)):
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41 | """
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42 | Set the 'data' (scantable) to work with.
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43 | Parameters:
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44 | scan: a scantable
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45 | mask: an optional mask retreived from scantable
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46 | edge: an optional number of channel to drop at
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47 | the edge of spectrum. If only one value is
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48 | specified, the same number will be dropped from
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49 | both sides of the spectrum. Default is to keep
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50 | all channels
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51 | """
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52 | if not scan:
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53 | raise RuntimeError, 'Please give a correct scan'
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54 | if len(edge)>2:
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55 | raise RuntimeError, "The edge parameter should have two \
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56 | or less elements"
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57 | if mask is None:
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58 | from numarray import ones
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59 | self.finder.setscan(scan,ones(scan.nchan()),edge)
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60 | else:
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61 | self.finder.setscan(scan,mask,edge)
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62 | return
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63 | def find_lines(self):
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64 | """
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65 | Search for spectral lines in the scan assigned in set_scan.
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66 | A number of lines found will be returned
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67 | """
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68 | return self.finder.findlines()
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69 | def get_mask(self,invert=False):
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70 | """
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71 | Get the mask to mask out all lines that have been found (default)
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72 |
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73 | Parameters:
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74 | invert if True, only channels belong to lines will be unmasked
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75 |
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76 | Note: all channels originally masked by the input mask or
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77 | dropped out by the edge parameter will still be excluded
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78 | regardless on the invert option
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79 | """
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80 | return self.finder.getmask(invert)
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81 | def get_ranges(self,defunits=True):
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82 | """
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83 | Get ranges (start and end channels or velocities) for all spectral
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84 | lines found.
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85 |
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86 | Parameters:
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87 | defunits if True (default), the range will use the same units
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88 | as set for the scan (e.g. LSR velocity)
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89 | if False, the range will be expressed in channels
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90 | """
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91 | return self.finder.getlineranges(defunits)
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