# Documentation

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# zgrid

Generate z-plane grid of constant damping factors and natural frequencies

## Syntax

```zgrid zgrid(z,wn) zgrid([],[]) ```

## Description

`zgrid ` generates, for root locus and pole-zero maps, a grid of constant damping factors from zero to one in steps of 0.1 and natural frequencies from zero to π in steps of π/10, and plots the grid over the current axis. If the current axis contains a discrete z-plane root locus diagram or pole-zero map, `zgrid` draws the grid over the plot without altering the current axis limits.

`zgrid(z,wn) ` plots a grid of constant damping factor and natural frequency lines for the damping factors and normalized natural frequencies in the vectors `z` and `wn`, respectively. If the current axis contains a discrete z-plane root locus diagram or pole-zero map,` zgrid(z,wn)` draws the grid over the plot. The frequency lines for unnormalized (true) frequencies can be plotted using

```zgrid(z,wn/Ts) ```

where `Ts` is the sample time.

`zgrid([],[]) ` draws the unit circle.

Alternatively, you can select Grid from the right-click menu to generate the same z-plane grid.

## Examples

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To see the z-plane grid on the root locus plot, type

`H = tf([2 -3.4 1.5],[1 -1.6 0.8],-1)`
```H = 2 z^2 - 3.4 z + 1.5 ------------------- z^2 - 1.6 z + 0.8 Sample time: unspecified Discrete-time transfer function. ```
```rlocus(H) zgrid axis equal```