source: trunk/python/asapmath.py@ 252

Last change on this file since 252 was 246, checked in by kil064, 20 years ago

in 'quotient' describe that ref can have one row

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  • Property svn:keywords set to Author Date Id Revision
File size: 10.9 KB
Line 
1from scantable import scantable
2
3def average_time(*args, **kwargs):
4 """
5 Return the (time) average of a scan or list of scans. [in channels only]
6 Parameters:
7 one scan or comma separated scans
8 mask: an optional mask (only used for 'var' and 'tsys' weighting)
9 scanav: False (default) averages all scans together,
10 True averages each scan separately
11 weight: Weighting scheme. 'none' (default), 'var' (variance
12 weighted), 'tsys'
13 Example:
14 # return a time averaged scan from scana and scanb
15 # without using a mask
16 scanav = average_time(scana,scanb)
17 # return the (time) averaged scan, i.e. the average of
18 # all correlator cycles
19 scanav = average_time(scan)
20
21 """
22 scanAv = False
23 if kwargs.has_key('scanav'):
24 scanAv = kwargs.get('scanav')
25#
26 weight = 'none'
27 if kwargs.has_key('weight'):
28 weight = kwargs.get('weight')
29#
30 mask = ()
31 if kwargs.has_key('mask'):
32 mask = kwargs.get('mask')
33#
34 lst = tuple(args)
35 from asap._asap import average as _av
36 for s in lst:
37 if not isinstance(s,scantable):
38 print "Please give a list of scantables"
39 return
40 return scantable(_av(lst, mask, scanAv, weight))
41
42def quotient(source, reference, preserve=True):
43 """
44 Return the quotient of a 'source' (signal) scan and a 'reference' scan.
45 The reference can have just one row, even if the signal has many. Otherwise
46 they must have the same number of rows.
47 Parameters:
48 source: the 'on' scan
49 reference: the 'off' scan
50 preserve: you can preserve (default) the continuum or
51 remove it. The equations used are
52 preserve - Output = Tref * (sig/ref) - Tref
53 remove - Output = Tref * (sig/ref) - Tsig
54 """
55 from asap._asap import quotient as _quot
56 return scantable(_quot(source, reference, preserve))
57
58def b_operate(left, right, op='add'):
59 """
60 Apply simple mathematical binary operations to two
61 scan tables, returning the result in a new scan table.
62 The operation is applied to both the correlations and the TSys data
63 Parameters:
64 left: the 'left' scan
65 right: the 'right' scan
66 op: the operation: 'add' (default), 'sub', 'mul', 'div'
67 """
68 from asap._asap import b_operate as _bop
69 return scantable(_bop(left, right, op))
70
71def scale(scan, factor, insitu=False, all=True):
72 """
73 Return a scan where all spectra are scaled by the give 'factor'
74 Parameters:
75 scan: a scantable
76 factor: the scaling factor
77 insitu: if False (default) a new scantable is returned.
78 Otherwise, the scaling is done in-situ
79 all: if True (default) apply to all spectra. Otherwise
80 apply only to the selected (beam/pol/if)spectra only
81 """
82 if not insitu:
83 from asap._asap import scale as _scale
84 return scantable(_scale(scan, factor, all))
85 else:
86 from asap._asap import scale_insitu as _scale
87 _scale(scan, factor, all)
88 return
89
90
91def add(scan, offset, insitu=False, all=True):
92 """
93 Return a scan where all spectra have the offset added
94 Parameters:
95 scan: a scantable
96 offset: the offset
97 insitu: if False (default) a new scantable is returned.
98 Otherwise, the addition is done in-situ
99 all: if True (default) apply to all spectra. Otherwise
100 apply only to the selected (beam/pol/if)spectra only
101 """
102 if not insitu:
103 from asap._asap import add as _add
104 return scantable(_add(scan, offset, all))
105 else:
106 from asap._asap import add_insitu as _add
107 _add(scan, offset, all)
108 return
109
110def convert_flux(scan, area, eta=1.0, insitu=False, all=True):
111 """
112 Return a scan where all spectra are converted to either Jansky or Kelvin
113 depending upon the flux units of the scan table.
114 Parameters:
115 scan: a scantable
116 area: the illuminated area of the telescope (m**2)
117 eta: The efficiency of the telescope (default 1.0)
118 insitu: if False (default) a new scantable is returned.
119 Otherwise, the conversion is done in-situ
120 all: if True (default) apply to all spectra. Otherwise
121 apply only to the selected (beam/pol/if)spectra only
122 """
123 if not insitu:
124 from asap._asap import convertflux as _convert
125 return scantable(_convert(scan, area, eta, all))
126 else:
127 from asap._asap import convertflux_insitu as _convert
128 _convert(scan, area, eta, all)
129 return
130
131def gain_el(scan, poly=None, filename="", method="linear", insitu=False, all=True):
132 """
133 Return a scan after applying a gain-elevation correction. The correction
134 can be made via either a polynomial or a table-based interpolation
135 (and extrapolation if necessary).
136 You specify polynomial coefficients, an ascii table or neither.
137 If you specify neither, then a polynomial correction will be made
138 with built in coefficients known for certain telescopes (an error will
139 occur if the instrument is not known).
140 Parameters:
141 scan: a scantable
142 poly: Polynomial coefficients (default None) to compute a gain-elevation
143 correction as a function of elevation (in degrees).
144 filename: The name of an ascii file holding correction factors.
145 The first row of the ascii file must give the column
146 names and these MUST include columns
147 "ELEVATION" (degrees) and "FACTOR" (multiply data by this) somewhere.
148 The second row must give the data type of the column. Use 'R' for
149 Real and 'I' for Integer. An example file would be:
150
151 TIME ELEVATION FACTOR
152 R R R
153 0.1 0 1.5
154 0.2 20 1.4
155 0.3 40 1.3
156 0.4 60 1.2
157 0.5 80 1.1
158 0.6 90 1.0
159 method: Interpolation method when correcting from a table. Values
160 are "nearest", "linear" (default), "cubic" and "spline"
161 insitu: if False (default) a new scantable is returned.
162 Otherwise, the conversion is done in-situ
163 all: if True (default) apply to all spectra. Otherwise
164 apply only to the selected (beam/pol/if)spectra only
165 """
166 if poly is None:
167 poly = ()
168 if not insitu:
169 from asap._asap import gainel as _gainEl
170 return scantable(_gainEl(scan, poly, filename, method, all))
171 else:
172 from asap._asap import gainel_insitu as _gainEl
173 _gainEl(scan, poly, filename, method, all)
174 return
175
176def opacity(scan, tau, insitu=False, all=True):
177 """
178 Return a scan after applying an opacity correction.
179 Parameters:
180 scan: a scantable
181 tau: Opacity from which the correction factor is exp(tau*ZD)
182 where ZD is the zenith-distance
183 insitu: if False (default) a new scantable is returned.
184 Otherwise, the conversion is done in-situ
185 all: if True (default) apply to all spectra. Otherwise
186 apply only to the selected (beam/pol/if)spectra only
187 """
188 if not insitu:
189 from asap._asap import opacity as _opacity
190 return scantable(_opacity(scan, tau, all))
191 else:
192 from asap._asap import opacity_insitu as _opacity
193 _opacity(scan, tau, all)
194 return
195
196def bin(scan, width=5, insitu=False):
197 """
198 Return a scan where all spectra have been binned up
199 width: The bin width (default=5) in pixels
200 insitu: if False (default) a new scantable is returned.
201 Otherwise, the addition is done in-situ
202 """
203 if not insitu:
204 from asap._asap import bin as _bin
205 return scantable(_bin(scan, width))
206 else:
207 from asap._asap import bin_insitu as _bin
208 _bin(scan, width)
209 return
210
211def average_pol(scan, mask=None, insitu=False):
212 """
213 Average the Polarisations together.
214 Parameters:
215 scan: The scantable
216 mask: An optional mask defining the region, where the
217 averaging will be applied. The output will have all
218 specified points masked.
219 insitu: If False (default) a new scantable is returned.
220 Otherwise, the averaging is done in-situ
221 Example:
222 polav = average_pols(myscan)
223 """
224 if mask is None:
225 mask = ()
226 if not insitu:
227 from asap._asap import averagepol as _avpol
228 return scantable(_avpol(scan, mask))
229 else:
230 from asap._asap import averagepol_insitu as _avpol
231 _avpol(scan, mask)
232 return
233
234def smooth(scan, kernel="hanning", width=5.0, insitu=False, all=True):
235 """
236 Smooth the spectrum by the specified kernel (conserving flux).
237 Parameters:
238 scan: The input scan
239 kernel: The type of smoothing kernel. Select from
240 'hanning' (default), 'gaussian' and 'boxcar'.
241 The first three characters are sufficient.
242 width: The width of the kernel in pixels. For hanning this is
243 ignored otherwise it defauls to 5 pixels.
244 For 'gaussian' it is the Full Width Half
245 Maximum. For 'boxcar' it is the full width.
246 insitu: If False (default) a new scantable is returned.
247 Otherwise, the scaling is done in-situ
248 all: If True (default) apply to all spectra. Otherwise
249 apply only to the selected (beam/pol/if)spectra only
250 Example:
251 none
252 """
253 if not insitu:
254 from asap._asap import smooth as _smooth
255 return scantable(_smooth(scan,kernel,width,all))
256 else:
257 from asap._asap import smooth_insitu as _smooth
258 _smooth(scan,kernel,width,all)
259 return
260
261def poly_baseline(scan, mask=None, order=0):
262 """
263 Return a scan which has been baselined (all rows) by a polynomial.
264 Parameters:
265 scan: a scantable
266 mask: an optional mask
267 order: the order of the polynomial (default is 0)
268 Example:
269 # return a scan baselined by a third order polynomial,
270 # not using a mask
271 bscan = poly_baseline(scan, order=3)
272 """
273 from asap.asapfitter import fitter
274 if mask is None:
275 from numarray import ones
276 mask = tuple(ones(scan.nchan()))
277 f = fitter()
278 f._verbose(True)
279 f.set_scan(scan, mask)
280 f.set_function(poly=order)
281 sf = f.auto_fit()
282 return sf
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