Scilab Function
Last update : April 1993

chart - Nichols chart

### Calling Sequence

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

### Parameters

- `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 number (see plot2d) for gain curves
  - `cphi`: color number (see plot2d) for phase curves

### Description

plot the Nichols'chart.

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,'(s^2+2*0.9*10*s+100)/(s^2+2*0.3*10.1*s+102.01)')
    chart(list(1,0,2,3));

    xbasc()
    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'])
    chart([-8 -6 -4],[80 120],list(1,0));