quiver
Quiver or velocity plot
Syntax
quiver(x,y,u,v)
quiver(u,v)
quiver(...,scale)
quiver(...,LineSpec)
quiver(...,LineSpec,'filled')
quiver(...,'PropertyName',PropertyValue,...)
quiver(ax,...)
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 components 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 specified in each corresponding
pair of elements in x and y.
The matrices x, y, u,
and v must all be the same size and contain corresponding
position and velocity components. However, x and y can
also be vectors, as explained in the next section. By default, the
arrows are scaled to just not overlap, but you can scale them to be
longer or shorter if you want.
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 automatic scaling. You can also tune the length of arrows after
they have been drawn by choosing the Plot Edit
tool, selecting the quiver object, opening the Property Editor, and
adjusting the Length slider.
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.
quiver(...,' specifies
property name and property value pairs for the quiver objects the
function creates. PropertyName',PropertyValue,...)
quiver(ax,...) plots into
the axes ax instead of into the current axes (gca).
h = quiver(...) returns
the Quiver object.
Expanding x- and y-Coordinates
MATLAB® expands 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.
Examples
Plot Vector Velocities
Use quiver to display an arrow at each data point in x and y such that the arrow direction and length represent the corresponding values in u and v.
[x,y] = meshgrid(0:0.2:2,0:0.2:2); u = cos(x).*y; v = sin(x).*y; figure quiver(x,y,u,v)
Show Gradient with Quiver Plot
Plot the gradient of the function .
[X,Y] = meshgrid(-2:.2:2); Z = X.*exp(-X.^2 - Y.^2); [DX,DY] = gradient(Z,.2,.2); figure contour(X,Y,Z) hold on quiver(X,Y,DX,DY) hold off
