# sgrid

s-plane grid lines.

## Calling Sequence

                sgrid()
                sgrid(zeta,wn [,colors])
                sgrid(['new',] zeta,wn [,colors])
                sgrid(zeta,wn [,'new'] [,colors])

## Arguments

zeta

  array of damping factors. Only values in `[0 1]` are taken into account. The default value is `[0 0.16 0.34 0.5 0.64 0.76 0.86 0.94 0.985 1]` .

wn

  array of natural frequencies in Hz. only positive values are taken into account. If not given it is computed by the program to fit with the boundaries of the plot.

colors

  a scalar or an 2 element array with integer values (color index).

## Description

Plots selected curves of constant damping ratio (selection given by `zeta`) and constant natural frequency (selection given by `wn`).

The `colors` argument may be used to assign a color for constant damping ratio curves (`colors(2)`) and for constant natural frequency curves (`colors(1)`).

The `sgrid` function is often used to draw a grid for evens root locus of continuous time linear systems. In such a case the `sgrid` function should be called after the call to evans. For discrete time linear systems one should use zgrid function instead.

The optional argument `'new'` can be used to erase the graphic window before plotting the grid.

## Examples

        //sgrid
        clf();sgrid(0:0.2:1,[0.2 0.6 1 1.7 2])

clf();sgrid(0:0.2:1,[0.2 0.6 1 1.7 2])

            H=syslin('c',352*poly(-5,'s')/poly([0,0,2000,200,25,1],'s','c'));
            clf();evans(H,100);sgrid()

H=syslin('c',352*poly(-5,'s')/poly([0,0,2000,200,25,1],'s','c')); clf();evans(H,100);sgrid()

## See Also

- evans
- zgrid
- datatips