Polar Plot RLim Not Working

I am currently plotting a graph of a certain radiation pattern. I do not want any negative radius values to be plotted. To "recitfy" this situationl, I utilized rlim. However, Negative values are still appearing. Thanks in advance.

This is my code:

theta = linspace(-10*pi,10*pi,10000);

rho = 10.*log10((cos(theta)).^9) + 30;

polarplot(theta, rho);

rlim([0 30]);

This is the graph: I do not wish to see the top and bottom lobes.

Answer 1

[Simon Chan]

Determine the index for non-negative number of rho only.

Beware your data are complex number.

theta = linspace(-10*pi,10*pi,10000);
rho = 10.*log10((cos(theta)).^9) + 30;
idx.pos = rho>=0;                               % Determine non-negative rho
polarplot(theta(idx.pos), rho(idx.pos));        

[Jon Ho]

Thank you for your help! Should I use polar pattern instead of polar plot for this kind of graph in the future?

[Simon Chan]

It really depends on what you would like to present.

For polar pattern, complex number is not allowed, below shows the magnitude plot.

Edit for Correction:

For polarpattern, the angle is in degree instead of radian, so I correct for this as follows:

V = polarpattern(rad2deg(theta),abs(rho))

[Jon Ho]

I see, this is the same shape as the polar plot that is not db scale and is not corrected to remove the negative values.

[Simon Chan]

Yes, the shape is the same.

Function polarpattern provides interactive data visualization and measurement.