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Frequency-domain response analysis for R
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DESCRIPTION
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README.md

README.md

freqr: Frequency-domain response analysis in R

Summary

A collection of R functions that enables the frequency-domain response analysis (FdRA) of dynamic systems. For a short introduction to FdRA have a look at this blog post.

Installation

devtools::install_github("pascalschulthess/freqr")

Functions and their usage

Bode plot

Takes the coefficients of a transfer function or the matrices A, B, C and D of a linear SISO state space representation and generates a Bode plot.

Usage

bodeplot(fr, fr.unit = NULL, n = NULL, d = NULL, A = NULL, B = NULL,
  C = NULL, D = NULL, highlight = NULL, label = NULL, as.period = F)

Example

In order to plot the transfer function

		 s^2 + 0.1s + 7.5
G(s) = ----------------------
		s^4 + 0.12s^3 + 9s^2

from 10^0 to 10^1 and add a highlight at 2 [rad/s], the function inputs take the form

bodeplot(fr = c(0, 1),
	      n = c(1, 0.1, 7.5),
	      d = c(1, 0.12, 9, 0, 0),
	      highlight = 2,
	      label = "Highlight")

and result in

Dependencies

library(pracma)
library(ggplot2)
library(dplyr)
library(grid)

Nyquist plot

Takes the coefficients of a transfer function and generates a Nyquist plot.

Usage

nyquistplot(fr, n = NULL, d = NULL)

Example

In order to plot the transfer function

		     100
G(s) = ----------------
		s^2 + 6s + 100

from 10^-2 to 10^3 the function inputs take the form

nyquistplot(fr = c(-2, 3), n = 100, d = c(1, 6, 100))

and result in

Dependencies

library(pracma)
library(ggplot2)

Sigma plot

Take the matrices A, B, C, and D of a linear MIMO state space representation and generate a sigma plot, i.e. a plot of the maximum and minimum singular values of the transfer function matrix evaluated over the frequency range.

Usage

sigmaplot(fr, fr.unit = NULL, A = NULL, B = NULL, C = NULL, D = NULL,
  as.period = F)

Example

In order to plot the state space represented by

                   / 0  1 |   1   0 \     
       / A | B \   |-1 -1 |   0   1 |
G(s) = |---|---| = |------|---------|
       \ C | D /   | 10 0 | 0.1   0 |
                   \  0 1 |   0 0.1 /

from 10^-2 to 10^2 the function inputs take the form

sigmaplot(fr = c(-2, 2),
		   A = matrix(c(0, 1, -1, -1), nrow = 2),
		   B = diag(2),
		   C = matrix(c(10, 0, 0, 1), nrow = 2),
		   D = 0.1*diag(2))

and result in

Dependencies

library(reshape2)
library(ggplot2)

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