1 # Nyquist plot with logarithmic amplitudes 2 3 This is a port of [Trond Andresen's MATLAB 4 version](https://www.mathworks.com/matlabcentral/fileexchange/7444-nyquist-plot-with-logarithmic-amplitudes) 5 for GNU Octave. To use it the 6 [control](https://gnu-octave.github.io/packages/control/) package needs to be 7 installed. 8 9 <div style="text-align: center;"> 10 <img src="nyqlog_octave_light.png" width="100%"> 11 <p align="center"><em>Nyquist plot with logarithmic amplitudes</em></p> 12 </div> 13 14 ## Quick start 15 16 Place the file `nyqlog.m` in Octave's path (see [Manipulating the Load 17 Path](https://docs.octave.org/v11.1.0/Manipulating-the-Load-Path.html)). Then 18 load the control package and define a transfer function. Finally call the 19 `nyqlog` function passing as argument the transfer function. 20 21 ```text 22 octave:1> pkg load control 23 octave:2> sys = zpk([-1/3 -1/2], [0 -0.02 -0.1 -2 -10], 48) 24 25 Transfer function 'sys' from input 'u1' to output ... 26 27 48 s^2 + 40 s + 8 28 y1: ------------------------------------------------ 29 s^5 + 12.12 s^4 + 21.44 s^3 + 2.424 s^2 + 0.04 s 30 31 Continuous-time model. 32 octave:3> nyqlog(sys) 33 ``` 34 35 ## Bonus: dark theme 36 37 This ported version of the function takes the colors from the variables defined 38 and used by Octave to render the figures: `defaultFigureColor` and 39 `defaultAxesXColor`. If you have customized these variables in Octave's 40 configuration file, the function will automatically use those colors as well. 41 42 <div style="text-align: center;"> 43 <img src="nyqlog_octave_dark.png" width="100%"> 44 <p align="center"><em>Nyquist plot with logarithmic amplitudes. Custom figure colors.</em></p> 45 </div> 46
