469,641 Members | 1,256 Online
Bytes | Developer Community
New Post

Home Posts Topics Members FAQ

Post your question to a community of 469,641 developers. It's quick & easy.

negative polar axis

hi!
how can i do polar plot in python with negative axes
that is the value of the magnitude is negative

Aug 13 '07 #1
3 2279
yadin wrote:
hi!
how can i do polar plot in python with negative axes
that is the value of the magnitude is negative
Surely a negative magnitude doesn't make sense in polar coordinates,
since the magnitude is supposed to represent the distance from the center.

About the best interpretation I can think of is to add 180 degrees to
the angle and reverse the sign of the magnitude, but this would be a
hack. Where are those coordinates coming from?

regards
Steve
--
Steve Holden +1 571 484 6266 +1 800 494 3119
Holden Web LLC/Ltd http://www.holdenweb.com
Skype: holdenweb http://del.icio.us/steve.holden
--------------- Asciimercial ------------------
Get on the web: Blog, lens and tag the Internet
Many services currently offer free registration
----------- Thank You for Reading -------------

Aug 13 '07 #2
Steve Holden wrote:
About the best interpretation I can think of is to add 180 degrees to
the angle and reverse the sign of the magnitude, but this would be a
hack. Where are those coordinates coming from?
Well, sometimes in polar coordinates (r, theta), r is allowed to be
negative. The usual translation from polar to Cartesian coordinates
makes this meaningful, albeit weird, so in effect the resulting
positions are just reflections around the origin.

Which I suppose is what the original poster was asking about, but it's
still not clear.

--
Erik Max Francis && ma*@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM, Y!M erikmaxfrancis
The conviction of wisdom is the plague of man.
-- Montaigne
Aug 13 '07 #3
On 10:58 Mon 13 Aug , Erik Max Francis wrote:
Steve Holden wrote:
About the best interpretation I can think of is to add 180 degrees to
the angle and reverse the sign of the magnitude, but this would be a
hack. Where are those coordinates coming from?

Well, sometimes in polar coordinates (r, theta), r is allowed to be
negative. The usual translation from polar to Cartesian coordinates
makes this meaningful, albeit weird, so in effect the resulting
positions are just reflections around the origin.

Which I suppose is what the original poster was asking about, but it's
still not clear.
Many years ago when I started programming machine tools (on punched
paper tape) if you wished to specify a cutter path around a radius as
being more than 180 degrees you programmed it as a negative r value.
There are 2 possible paths from x1y1 to x2y2 along a radius r and going
in the same direction; that less than 180 deg and that more than 180
deg, unless the radius is exactly 180. But this was rarely used, the
other method of specifying the end point as an incremental value in
relation to the radius centre is less error prone when the arcs are
close to 180.

Sorry about the slight diversion but I'm getting nostalgic.

Regards, John
--
War is God's way of teaching Americans geography
Ambrose Bierce (1842 - 1914)
Aug 13 '07 #4

This discussion thread is closed

Replies have been disabled for this discussion.

Similar topics

14 posts views Thread by Google Mike | last post: by
3 posts views Thread by parrot toes | last post: by
3 posts views Thread by Jeremy Chapman | last post: by
10 posts views Thread by schaefer.mp | last post: by
3 posts views Thread by afrogazer | last post: by
reply views Thread by gheharukoh7 | last post: by
By using this site, you agree to our Privacy Policy and Terms of Use.