Summary

Source code

This graphics has been realized with the help of the following Octave script:

order = 4;
pointNb = 100;
axesLength = 1.25;
textOffset = 0.05;

angle = linspace(pi/2, 3*pi/2, pointNb);
poleAngles = pi/2 + pi * [1:order]/order - pi/(2*order);
poles = cos(poleAngles) + i * sin(poleAngles);

figure(1);
plot(cos(angle), sin(angle));
hold on;
plot([-axesLength, axesLength-1], [0, 0], 'k');
plot([0, 0], [-axesLength, axesLength], 'k');
plot(poles, 'xr');
hold off;
axis("equal", "off");
text(axesLength-1+textOffset, textOffset, "re(s)");
text(textOffset, axesLength+textOffset, "im(s)");
print -dsvg butterworth_poles_4.svg

Licensing

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You are free:

• to share – to copy, distribute and transmit the work
• to remix – to adapt the work

Under the following conditions:

• attribution – You must give appropriate credit, provide a link to the license, and indicate if changes were made. You may do so in any reasonable manner, but not in any way that suggests the licensor endorses you or your use.
• share alike – If you remix, transform, or build upon the material, you must distribute your contributions under the same or compatible license as the original.

https://creativecommons.org/licenses/by-sa/3.0CC BY-SA 3.0 Creative Commons Attribution-Share Alike 3.0 truetrue