limiting theta in polar axis plots

Is there any way to limit the theta extent in a polar axis plot?

There are a variety of angular contexts in which 360 degrees are not necessary. To convey the orientation of an undirected line, you need only 0-180 degrees. The minimum separation between two intersecting lines only ranges from 0-90 degrees.

It seems like the ideal way for this to work would be to have a function analogous to xlim(), maybe called thetalim(thetamin, thetamax), and then treat the two bounding radial lines as the primary and secondary y axes.

Didn’t see anything like this in any of the examples or documentation though. If it’s not possible now, I think it would be a wonderful addition.

Thanks,

Zane

···

Zane Selvans

Amateur Earthling

zane@…1923…

303/815-6866

http://zaneselvans.org

PGP Key: 55E0815F

No, it's not possible now. Just so I'm clear -- you're suggesting plotting on a wedge from theta_1 to theta_2? Seems doable with a little work.

Mike

Zane Selvans wrote:

···

Is there any way to limit the theta extent in a polar axis plot?

There are a variety of angular contexts in which 360 degrees are not necessary. To convey the orientation of an undirected line, you need only 0-180 degrees. The minimum separation between two intersecting lines only ranges from 0-90 degrees.

It seems like the ideal way for this to work would be to have a function analogous to xlim(), maybe called thetalim(thetamin, thetamax), and then treat the two bounding radial lines as the primary and secondary y axes.

Didn't see anything like this in any of the examples or documentation though. If it's not possible now, I think it would be a wonderful addition.

Thanks,
Zane


Zane Selvans
Amateur Earthling
zane@…1923… <mailto:zane@…1923…>
303/815-6866
http://zaneselvans.org
PGP Key: 55E0815F

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Michael Droettboom
Science Software Branch
Operations and Engineering Division
Space Telescope Science Institute
Operated by AURA for NASA

Yes, exactly. For instance if I wanted to make a polar bar chart showing the distribution of angles separating a collection of lines at their intersections, I would only need to display one quarter of the polar plot, the first quadrant, from 0-90 degrees. If I wanted to display the orientation of, say, a fault on the surface of the Earth, I’d need 180 degrees, but I might want to use the northern half of the circle (orientations ranging from West to East (-90, 90)) or perhaps the eastern half (ranging from (0, 180)).

Ideally, the user would be able to specify both thetamin and thetamax, and also an offset describing the location of theta=0, because in some applications it doesn’t make sense for zero to be in its traditional polar-coordinates location at the right hand side. E.g. in a geographic context, where the angles being displayed are compass headings, it is traditional to put zero (north) at the top. Putting zero at the top would also make sense if you were plotting data that corresponded to angular deviations to the left and right from some specified path.

Some portion of this functionality has been implemented in the “windrose” module, see:

http://youarealegend.blogspot.com/2008/09/windrose.html

http://www.nabble.com/windrose-OO-td16298025.html

but with a mind toward a particular kind of application (windrose diagrams obviously :). But I think allowing users to specify (thetamin, thetamax, offset) would be a very generally applicable improvement.

Thanks again,

Zane

···

On Oct 17, 2008, at 11:06 AM, Michael Droettboom wrote:

No, it’s not possible now. Just so I’m clear – you’re suggesting plotting on a wedge from theta_1 to theta_2? Seems doable with a little work.

Zane Selvans

Amateur Earthling

zane@…1923…

303/815-6866

http://zaneselvans.org

PGP Key: 55E0815F