# chart

Nichols chart

## Calling Sequence

    chart([flags])
                chart(gain [,flags])
                chart(gain,phase [,flags])

## Arguments

gain

  real vector ( gains (in DB))

phase

  real vector (phases (in degree))

flags

  a list of at most 4 flags list(sup [,leg [,cm [,cphi]]])

  sup

    1 indicates superposition on the previous plot 0 no superposition is done

  leg

    1 indicates that legends are drawn, o: no legends

  cm

    color index for gain curves

  cphi

    color index for phase curves

## Description

plot the Nichols'chart: iso-gain and iso-phase contour of y/(1+y) in phase/gain plane

`chart` may be used in cunjunction with black.

The default values for `gain` and `phase` are respectively :

`[-12 -8 -6 -5 -4 -3 -2 -1.4 -1 -.5 0.25 0.5 0.7 1 1.4 2 2.3 3 4 5 6 8 12]`

`[-(1:10) , -(20:10:160)]`

## Examples

    s=poly(0,'s')
    h=syslin('c',(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01))
    black(h,0.01,100)
    chart(list(1,0,2,3));

    clf()
    h1=h*syslin('c',(s^2+2*0.1*15.1*s+228.01)/(s^2+2*0.9*15*s+225))
    black([h1;h],0.01,100,['h1';'h'])
    set(gca(),'data_bounds',[-180 -30;180 30]) //enlarge the frame
    chart(list(1,0));

## See Also

- nyquist
- black