Clip

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3.4.2.3 Clip

mode                =     ’clip’        #  Flagging mode (list/manual/clip/shadow/quack/
                                        #  elevation/tfcrop/rflag/extend/unflag/summary)
...
     datacolumn     =     ’DATA’        #  Data column on which to operate
                                        #   (data,corrected,model,residual)
     clipminmax     =         []        #  Range to use for clipping
     clipoutside    =       True        #  Clip outside the range, or within it
     channelavg     =      False        #  Average over channels (scalar average)
     clipzeros      =      False        #  Clip zero-value data

in addition to the regular selection parameters, mode=’clip’ also has an option to select between the DATA, CORRECTED_DATA and other scratch columns for operation. clipminmax selects the range of values to be clipped – usually this is combined with clipoutside=True to clip everything but the values coverd in clipminmax. The data can also be averaged over the selected spw channel ranges by setting channelavg=True. clip will also flag ’NaN’, ’inf’, and ’-inf’ values by default and can flag exact zero values (these are sometimes produced by the JVLA correlator) using the clipzeros parameter.

Note : For modes clip, tfcrop and rflag, channel-ranges can be excluded from flagging by selecting ranges such as spw=’0:0 ~
5 ;10 ~
6 3’. This is a way to protect known spectral-lines from being flagged by the autoflag algorithms.

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