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Scilab help >> CACSD > Plot and display > zgrid

# zgrid

zgrid plot

### Calling Sequence

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

### Arguments

zeta

array of damping factors. Only values in [0 1] are taken into account. The default value is 0:0.1:1.

wn

array of normalized natural frequencies (factors of π/dt). Only values in [0 1] are taken into account. The default value is 0:0.1:1.

colors

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

### Description

plots z-plane grid lines: lines of constant damping factor (selection given by zeta) and natural frequency (selection given by wn) are drawn in within the unit Z-plane circle.

Iso-frequency curves are shown in on the interval [0,%pi/dt].

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

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

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

### Examples

//zgrid
clf();zgrid(0:0.2:1,[0.2 0.6 0.8 1])

//zgrid with discrete time system  root locus
z=poly(0,'z')
H=syslin(0.01,(0.54-1.8*z+2.9*z^2-2.6*z^3+z^4)/(0.8+0.78*z-0.1*z^2+0.9*z^3+z^4))
clf();evans(H,1000);zgrid(0:0.1:0.5)

### See Also

• evans — Evans root locus
• sgrid — s-plane grid lines.
• freson — peak frequencies
• datatips — Tool for placing and editing tips along the plotted curves.
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