# Polar axes in Octave?

if i draw a polar plot with Octave the axes are cartessian, not polar axes. But in Matlab it seems polar axes exists for polar plots. Is there anyway to draw with polar axes in polar plots in Octave? Thanks

• I can rationalize the "Cartesian" axes on a polar plot as displaying the increments of angle $\theta = 0,\pi/2,\pi, 3\pi/2$ for polar coordinate $\theta$. Do you mean that concentric circles denoting radius $r \gt 0$ are missing? (Note that ticks along the "Cartesian" axes serve much the same purpose.)
– hardmath
Nov 4, 2013 at 17:40
• Yeah, but with polar axes is a good view for teaching the polar coordinates Nov 4, 2013 at 21:12
• I'm really asking what you mean by "polar axes". A graph of polar coordinates might have additional rays or lines through the origin to illustrate constant $\theta$ loci and/or circles centered at the origin to illustrate constant $r$ (radius). Do you have both in mind?
– hardmath
Nov 4, 2013 at 21:43
• Ah ok, sorry, sometimes I don't understenand the meanin' in english. Well, I want something like the image on this webpage where it puts Examples-> A simple polar plot mathworks.es/es/help/matlab/ref/polar.html Nov 5, 2013 at 6:40

## 2 Answers

Older versions of Octave used gnuplot as the graphics engine, and you can still fall back on that capability. A StackOverflow post from 2011 illustrates gnuplot's capabilities, including some concentric circles around the origin.

A 2005 mailing list thread discusses Octave commands to "set" a polar grid (the phrase I'd rather use than "polar axes").

You'll probably want to know how to get those circles with the high-level interface, so you won't have to rely on the gnuplot commands. However as recently as last year, according to this mailing list thread, support for polar grids in the OpenGL library was still lacking.

This 2008 Help-octave mailing list thread discusses the missing polar grid but mentions at the end an Octave toolkit, octave-epstk, using encapsulated postscript (EPS), that is supposed to provide the missing polar grid. Unfortunately EpsTk seems to have lost their homepage in Germany, but the toolkit itself is still available in Debian and Ubuntu, and likely in other such Linux distros.

• Thanks, epsTk works good to me. I put below a simple code. Nov 5, 2013 at 17:37

I put a simple code using epstk

theta = 0:0.01:2*pi;
rho = sin(2*theta).*cos(2*theta);

eopen('polar.eps') %make a eps file

epolar(theta,rho,'Polar Function',0,[0 0 1],1.5)
%plot in the eps file our function with polar coordinates

eclose; %close eps file
eview % we show the eps file with gsview or a browser.


And the result