Converting a linear equation to decibel

I'm trying to convert a linear polar plot to decibel but I don't know how to proceed. Here is the original:

theta = 2*pi*linspace(0, 1, 30);
r = cos(theta/2).^2;
polar(theta, r, 'r-');

This is my progress so far:

theta = 2*pi*linspace(0, 1, 30);
r = 10*log10(abs(cos(theta/2).^2));
b = find(r(-40))
b == -40
b = b + 40 
polardb(theta, r, -40, 'r-');

I don't know how to proceed.

Answer 1

[Star Strider]

The ‘theta’ vector likely needs to have more points, however that appears to be correct.

I use a slightly different approach here —

theta = 2*pi*linspace(0, 1, 30);
r = cos(theta/2).^2;

figure
polarplot(theta, r, 'r-')
title('r(\theta)')

figure
polarplot(theta, mag2db(r), 'r-')
title('r(\theta) (dB)')
rt = rticklabels;
rticklabels(cellfun(@(x)sprintf('%s dB',x),rt', 'Unif',0))

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[flanker989]

That helped alot, thank you.

[Star Strider]

My pleasure!

If my Answer helped you solve your problem, please Accept it!

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