The first data container accum'ed in a buffer is used as a ; template for that buffer and subsequent data containers accum'ed to ; that buffer must match in number of channels. On subsequent uses of ; accum, a warning is printed if the channel spacing ; (frequency_interval) or frequency resolution differs from the values ; already in the buffer. The accumulation proceeds even when a ; warning is printed. Use resample to change the frequency_interval ; and gsmooth to change the frequency_resolution. ; ;
There are four accum buffers available to this and related ; GUIDE-layer procedures. Users can use these to have several ; averages proceeding simultaneously, but separately, when it is useful ; to do so (e.g. polarizations). Use the accumnum keyword to specify ; which buffer to use (defaults to 0). ; ;
The default weight for each spectrum is ; exposure*frequency_resolution/Tsys^2. A different weight can be ; given using the weight keyword. Alternatively, each channel can be ; given a separate weight by providing a vector of weights in the ; weight argument. In that case, the number of elements in weight ; must be the same as in the data. This can be used to re-start an ; accum from a previous average where the weight was retrieved from ; that average. See ave for more details. See dcaccum for ; additional information on how the header parameters are weighted ; during the accumulation. ; ;
Blanked channels (Not a Number data values) are excluded from the ; average. An entirely blanked spectrum (all values are NaNs - e.g. bad ; lags from the GBT spectrometer) is completely ignored by the ; accumulation (the contents of that accum buffer are unchanged). ; ; @param accumnum {in}{optional}{type=integer}{default=0} accum buffer. ; Defaults to the primary buffer (accumnum = 0). There are 4 buffers ; in all so this value must be between 0 and 3, inclusive. ; ; @keyword weight {in}{optional}{type=float} The weight to use for ; averaging this data. If not set, a weight of ; exposure*frequency_resolution/Tsys^2 is used. This can also be a ; vector of weights, one per channel. ; ; @keyword dc {in}{optional}{type=spectrum or integer} The data ; container to accum. If not supplied, use the PDC. If this is an ; integer, then use the data container at that buffer number in !g.s. ; ; @examples ; A simple averaging operation: ;
; sclear ; getrec,1 ; accum ; getrec,2 ; accum ; ave ;;
; Average two polarizations separately for some position switched scans ;
; sclear ; clears accum buffer 0 ; sclear, 1 ; clears accum buffers 1 ; getps,32,plnum=0 ; accum, 0 ; getps,32,plnum=1 ; accum, 1 ; getps,34,plnum=0 ; accum, 0 ; getps,34,plnum=1 ; accum, 1 ; ave,1 ; Average plnum=1 data and store ; ; the result in the PDC ; copy,0,1 ; Copy the result to DC 1 ; ave, 0 ; Average plnum=0 data ; oshow, 1 ; Overplot the plnum=1 average ;;
; Average some data, remember the vector weights at the average, and ; then average some more data. ;
; sclear ; getrec,1 ; accum ; getrec,2 ; accum ; ave, wtarray=wtave1_3 ; copy, 0, 10 ; save average for later use ; sclear ; no necessary, but better to be sure ; getrec,3 ; accum ; getrec,4 ; accum ; ave, wtarray=wtave3_4 ; copy, 0, 11 ; save this for later use ; ; other things could happen here ; ; average 11 and 10 using appropriate weighting ; ; they might not be scalars if some part of each was flagged or ; ; blanked ; sclear ; accum, dc=10, weight=wtave1_3 ; accum, dc=11, weight=wtave3_4 ; ave, wtarray=wtave_all4 ;; ; @uses data_valid ; @uses dcaccum ; ; @version $Id$ ;- pro accum, accumnum, weight=weight, dc=dc compile_opt idl2 on_error, 2 if not !g.line then begin message,'Can not accumulate continuum data, sorry.',/info return endif if n_elements(accumnum) eq 0 then accumnum = 0 if (accumnum lt 0 or accumnum gt 3) then begin message,'accumnum must be in the range 0 to 3',/info return endif accumbuf = !g.accumbuf[accumnum] if n_elements(dc) eq 0 then begin thisdc = !g.s[0] endif else begin thisdc = dc endelse if size(thisdc,/type) ne 8 then begin ; interpret it as a buffer number if thisdc lt 0 or thisdc ge n_elements(!g.s) then begin message,string(n_elements(!g.s),format='("dc buffer must be between 0 and ",i2)'),/info return endif thisdc = !g.s[thisdc] endif dataOk = data_valid(thisdc,name=name) if dataOk le 0 then begin message,'No valid data found to accum',/info return endif if name ne 'SPECTRUM_STRUCT' then begin message,'data container is not a SPECTRUM_STRUCT',/info return endif dcaccum, accumbuf, thisdc, weight=weight !g.accumbuf[accumnum] = accumbuf end