| Re: circles [message #9566 is a reply to message #9519] |
Wed, 16 July 1997 00:00   |
pit
Messages: 92
Registered: January 1996
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Member |
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In article <5qd140$ckk$1@gwdu19.gwdg.de>,
pit@re.uni-sw.gwdg.de (Peter Suetterlin) writes:
> In article <33C6A55C.E92FBB0D@kprwww.na.astro.it>,
> Kevin Reardon <kreardon@kprwww.na.astro.it> writes:
>> The previous suggestion by Peter Suetterlin (pit@uni-sw.gwdg.de) of:
>> img = (shift(dist(X,Y),x0,y0)) LT R
>> doesn't seem to work if x0 and y0 are not equal to X/2 and Y/2
>> (i.e. the circle is not centerted) because of wrapping problems when
>> the array is shifted.
>
> Strange, what system/version are you using?
> I checked it before posting, and just again on three different systems
> (Linux, SunOS, HP-UX) with IDL 4.01 and 3.0.0:
Yes, Kevin was right, my suggestion doesn't work in all cases, as he
wrote me by email:
The radius R of the circle has to be smaller than the shift amounts x0
and y0, and also smaller than (X-x0) and (Y-y0), or the edge-wraping of
the SHIFT function will produce strange results. Sorry :-/
Peter
--
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Peter "Pit" Suetterlin http://www.uni-sw.gwdg.de/~pit
Universitaets-Sternwarte Goettingen
Tel.: +49 551 39-5048 pit@uni-sw.gwdg.de
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