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
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.
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