svplot singular-value sigma-plot

## Syntax

                SVM = svplot(sl)
                SVM = svplot(sl, w)

## Arguments

sl

  `syslin` list (continuous, discrete or sampled system)

w

  real vector (optional parameter)

## Description

computes for the system `sl=(A,B,C,D)` the singular values of its transfer function matrix:

                 G(jw) = C(jw*I-A)B^-1+D
    or
                 G(exp(jw)) = C(exp(jw)*I-A)B^-1+D
    or
                 G(exp(jwT)) = C(exp(jw*T)*I-A)B^-1+D

evaluated over the frequency range specified by `w`. (T is the sampling period, `T=sl('dt')` for sampled systems).

`sl` is a `syslin` list representing the system `[A,B,C,D]` in state-space form. `sl` can be continuous or discrete time or sampled system.

The `i`-th column of the output matrix `SVM` contains the singular values of `G` for the `i`-th frequency value `w(i)`.

    SVM = svplot(sl)

is equivalent to

    SVM = svplot(sl,logspace(-3,3))  (continuous)

    SVM = svplot(sl,logspace(-3,%pi)) (discrete)

## Examples

    x = logspace(-3,3);
    y = svplot(ssrand(2,2,4),x);
    clf()
    plot2d("ln", x, 20*log(y')/log(10))
    xgrid(12)
    xtitle("Singular values plot","(Rd/sec)", "Db");

x=logspace(-3,3); y=svplot(ssrand(2,2,4),x); clf() plot2d("ln", x, 20*log(y')/log(10)) xgrid(12) xtitle("Singular values plot","(Rd/sec)", "Db");