Re: circle plot symbol

[Craig Markwardt <craigmnet(at)cow.physics.wisc.edu>]

davidf@dfanning.com (David Fanning) writes:

> Craig Markwardt (craigmnet@cow.physics.wisc.edu) writes:
> > 
> > refik@rsmas.miami.edu (Refik Orhun) writes:
> > 
> > 
> > > Hi Folks,
> > > 
> > > First of all, you have quite an impressive news group.  
> > > Well, I Have a simple question.  How do I code a circle as a symbol in a
> > > plot ?  All the symbols in my plots so far are squares, diamonds and
> > > triangles, i.e. codes 2, 3, 4, etc...
> > > 
> > > Can anybody tell me the number or code for a "simple circle" to use
> > > in PSYM= ?
> > 
> > I don't think a circle symbol exists, but I'm sure I will be
> > corrected.  You can use the following procedure to define a circle as
> > the "user" symbol, symbol 8.  You call it either as plain "circsym" or
> > as "circsym, /filled" to get a filled circle.  Then you can say,
> > "plot, ..., psym=8"
> > 
> > pro circsym, _EXTRA=extra
> >   theta=findgen(26)*0.251327412
> >   usersym, cos(theta), sin(theta), _EXTRA=extra
> > end
> > 
> > I believe somebody has a big library of these kinds of user-defined
> > symbols.
> 
> The problem with this solution (and I've used it myself)
> is that as often as not the "circles" show up as ellipses. :-)

Sorry David, I'll disagree with you on this one.  If you use USERSYM
to make the circle, then it should come out circular every time.

I agree if you simply do "plot, cos(th), sin(th)", it can come out
elliptical, but as a USERSYM, IDL automatically does the data scaling.

Craig

-- 
--------------------------------------------------------------------------
Craig B. Markwardt, Ph.D.         EMAIL:    craigmnet@cow.physics.wisc.edu
Astrophysics, IDL, Finance, Derivatives | Remove "net" for better response
--------------------------------------------------------------------------