[daip] CLIP and FLGIT ?

[Eric Greisen]

Nissim Kanekar wrote:

> Had a couple of suggestions about tasks CLIP and FLGIT in AIPS and 
> thought I should pass them on. The feature in CLIP that allows all 
> channels to be flagged if the values in some are above some threshold 
> [APARM (7) and (9)] is really nice for spectral line work (as it means 
> that there's no channel-dependent flagging, so the noise is constant 
> across the band). Of course, one would like to apply such a threshold to 
> the central parts of the band and then use it to flag all channels. 
> Right now, the only control over the channel range is with BCHAN and 
> ECHAN, which only select the group of channels to be worked with (i.e. 
> the flags are only applied to this group of channels). It would be great 
> to have an ICHANSEL adverb in CLIP to allow selection of a range of 
> channels for the application of the above threshold.
> 
> FLGIT is very nice as well, and does have the possibility of selection 
> with ICHANSEL; however,  it doesn't have the feature allowing all 
> channels to be flagged if the values in some are above some threshold 
> [APARM (7) and (9) in CLIP]. Could this be added ?

CLIP examines BCHAN through ECHAN but flags every channel when too many 
channels in the BCHAN to ECHAN range are flagged already.  I did change 
the flag +-n channels option to go outside BCHAN and ECHAN if needed to 
get the n channels and not go outside the full spectrum.

I have also changed FLGIT to add options to the flag +- n channels about 
a bad channel and to flag all channels if >= m are flagged.  Note that 
FLGIT looks at all channels for some operations like APARM(1) - ICHANSEL 
selects the channels for the linear fit and the median window.

Tomorrow's MNJ will bring these changes.

Eric Greisen