[daip] Minor IMAGR.HLP issue

[Eric Greisen]

Craig Walker writes:
 > Just thought I'd pass this on while I'm noticing it.
 > 
 > IMAGR.HLP says:
 >    ECHAN......Highest channel number to to include in image,
 >               0 => max   The actual # of output channels will be
 >                    (BCHAN-ECHAN+1-NCHAV)/CHINC + 1

     Yes this was a typo - it is ECHAN-BCHAN - but otherwise the
formula is correct.

 > The equation is surely wrong --- for most combinations of parameters, it 
 > will be negative.  Also I suspect that NCHAV is not in correctly (if it 
 > is, then I have totally misinterpreted what NCHAV does).

      Probably.

 > 
 > The correct equation depends how CHINC and NCHAV interact, which I don't 
 > feel I understand from the help file.  The help file says:  "If NCHAV>1, 
 > CHINC refers to the first plane going into the map.".  That still 
 > doesn't tell me if CHINC is applied to pre or post average channels.  In 
 > fact, I'm not sure what it does tell me.
 > 
 > What happens if ECHAN-BCHAN+1 is not divisible by NCHAV?

     The last output channel has fewer input channels.

 > 
 > Here is a guess for the actual number of output channels, assuming any 
 > partial averages are skipped and CHINC applies to output channels.  I 
 > would not be surprised if these assumptions are wrong.
 > 
 >            ((ECHAN-BCHAN+1)/NCHAV)/CHINC

No.

CHINC applies to input channels and may be > NCHAV or < NCHAV if the
user wishes.

I have added stuff to the help file and fixed the typo.  You are the
first to complain about these very old wordings.

Eric Greisen