# Re: circle plot symbol

```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. :-)

For a really good circle procedure, I like to use TVCIRCLE
from the NASA Goddard library. It does the data coordinate
correction for you so that circles always show up as circles.
page:

http://www.dfanning.com/tips/make_circle.html

Cheers,

David
--
David Fanning, Ph.D.
Fanning Software Consulting
Phone: 970-221-0438 E-Mail: davidf@dfanning.com
Coyote's Guide to IDL Programming: http://www.dfanning.com/
Toll-Free IDL Book Orders: 1-888-461-0155

```