MATLAB Function Reference
quiver

Quiver or velocity plot

Syntax

• ```quiver(U,V,U,V)
quiver(X,Y)
quiver(...,scale)
quiver(...,`LineSpec`)
quiver(...,`LineSpec``,`'filled')
h = quiver(...)
```

Description

A quiver plot displays velocity vectors as arrows with components (`U`,`V`) at the points (`X`,`Y`).

For example, the first vector is defined by componets `U(1)`,`V(1)` and is displayed at the point `X(1)`,`Y(1)`.

```quiver(X,Y,U,V) ``` plots vectors as arrows at the coordinates specifide in each corresponding pair of elements in `X` and `Y`. The matirces `X`, `Y`, `U`, and `V` must all be the same size and contain corresponding position and velocity components.

Expanding X and Y Coordinates

MATLAB expandes `X` and `Y`, if they are not matrices. This expansion is equivalent to calling `meshgrid` to generate matrices from vectors:

• ```[X,Y] = `meshgrid`(X,Y)
quiver(X,Y,U,V)
```

In this case, the following must be true:

`length(X)` `=` `n` and `length(Y)` `=` `m`, where `[m,n]` `=` `size(U)` `=` `size(V)`

The vector `X` corresponds to the columns of `U` and `V`, and vector `Y` corresponds to the rows of `U` and `V`.

```quiver(U,V) ``` draws vectors specified by `U` and `V` at equally spaced points in the x-y plane.

```quiver(...,scale) ``` automatically scales the arrows to fit within the grid and then stretches them by the factor `scale`. `scale` `=` `2` doubles their relative length and `scale` `=` `0.5` halves the length. Use `scale = 0` to plot the velocity vectors without the automatic scaling.

```quiver(...,LineSpec) ``` specifies line style, marker symbol, and color using any valid `LineSpec`. `quiver` draws the markers at the origin of the vectors.

```quiver(...,LineSpec,'filled') ``` fills markers specified by `LineSpec`.

```h = quiver(...) ``` returns a vector of line handles.

Examples

Plot the gradient field of the function.

• ````[X,Y]` `=` `meshgrid````(-2:.2:2);
````Z` `=` `X.`*```exp(-X.^2 - Y.^2);
```[DX,DY] = `gradient`(Z,.2,.2);
`contour`(X,Y,Z)
`hold` on
quiver(X,Y,DX,DY)
colormap hsv
`grid` off
hold off

```

`contour`, `LineSpec`, `plot`, `quiver3`