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compass

Arrows emanating from origin

  • Circular grid with arrows emanating from the origin

Description

example

compass(U,V) plots arrows originating from the point (0, 0). Specify the direction of arrows using the Cartesian coordinates U and V, with U indicating the x-coordinates and V indicating the y-coordinates. The number of arrows matches the number of elements in U.

The compass function plots arrows on a circular grid with theta-axis and r-axis tick labels within an Axes object. Therefore, the coordinates you specify do not match the labels displayed on the plot.

example

compass(Z) plots arrows using the real and imaginary parts of the complex values specified by Z, with the real part indicating the x-coordinates and the imaginary part indicating the y-coordinates. This syntax is equivalent to compass(real(Z),imag(Z)).

example

compass(___,LineSpec) sets the line style, marker symbol, and color for the arrows.

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compass(ax,___) plots arrows in the specified axes instead of the current axes.

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c = compass(___) returns a vector of Line objects. This syntax is useful for controlling the appearance of arrows.

Examples

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Create a compass plot by specifying the Cartesian coordinates of each arrow.

u = [5 3 -4 -3 5];
v = [1 5 3 -2 -6];
compass(u,v)

Create a compass plot using polar coordinates by first converting them to Cartesian coordinates.

To do this, specify data using polar coordinates. Convert them to Cartesian coordinates using the pol2cart function. Then, create the plot.

th = linspace(pi/4,2*pi,10);
r = linspace(5,20,10);
[u,v] = pol2cart(th,r);
compass(u,v)

Note that the theta-axis and r-axis tick labels correspond to the polar coordinates.

Sample a sinusoid at equally spaced intervals. Then, compute the 10-point discrete Fourier transform of the sinusoid. The result is a vector of complex values.

t = linspace(0,8*pi,100);
y = sin(2*t) + 2*sin(t+pi/2);
f = fft(y,10);

Display the complex values using a compass plot. The real part determines the x-coordinate of each arrow, and the imaginary part determines the y-coordinate.

compass(f)

Create a compass plot with red arrows.

u = [5 3 -4 -3 5];
v = [1 5 3 -2 -6];
compass(u,v,'r')

Specify the line width and color of a single arrow by assigning the arrow to a variable and then setting its properties. To do this, first create a compass plot and return an array of Line objects.

u = [3 5 -4 -3 5];
v = [5 1 3 -2 -6];
c = compass(u,v);

Assign the first arrow to a variable. The first arrow corresponds to the first elements of u and v. Then, change the line width and color.

c1 = c(1);
c1.LineWidth = 2;
c1.Color = 'r';

Rotate a compass plot so that 0 degrees points up by using the view function.

To do this, create a compass plot using polar coordinates. Convert the polar coordinates to Cartesian coordinates by using the pol2cart function, and then plot the converted coordinates.

th = linspace(0,3*pi/2,10);
r = linspace(5,20,10);
[u,v] = pol2cart(th,r);
compass(u,v)

Note that 0 degrees points to the right. Rotate the theta-axis 90 degrees in a counterclockwise direction by calling view and specifying the first argument as -90. Maintain the 2-D view by specifying the second argument as 90.

view(-90,90)

Note that 0 degrees now points up.

Starting in R2019b, you can display a tiling of plots using the tiledlayout and nexttile functions. Call the tiledlayout function to create a 1-by-2 tiled chart layout. Call the nexttile function to create an axes object and return the object as ax1. Create the left plot by passing ax1 to the compass function. Add a title to the plot by passing the axes to the title function. Repeat the process to create the right plot.

u = [7 5 -2 -5 8];
tiledlayout(1,2)

% Left plot
ax1 = nexttile;
v1 = [3 7 5 -4 -6];
compass(ax1,u,v1)
title(ax1,'Left Plot')

% Right plot
ax2 = nexttile;
v2 = [-3 -4 -5 6 6];
compass(ax2,u,v2)
title(ax2,'Right Plot')

Input Arguments

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x-coordinates, specified as a scalar, vector, or matrix. Specify Cartesian values. To convert data from polar to Cartesian, use pol2cart.

The size of U must match the size of V.

y-coordinates, specified as a scalar, vector, or matrix. Specify Cartesian values. To convert data from polar to Cartesian, use pol2cart.

The size of V must match the size of U.

Complex values, specified as a scalar, vector, or matrix. The real part of Z indicates the x-coordinates of arrows, and the imaginary part indicates the y-coordinates.

Line style, marker, and color, specified as a character vector or string containing symbols. The symbols can appear in any order. You do not need to specify all three characteristics (line style, marker, and color). For example, if you omit the line style and specify the marker, then the plot shows only the marker and no line.

Example: '--or' is a red dashed line with circle markers

Line StyleDescription
-Solid line
--Dashed line
:Dotted line
-.Dash-dot line
MarkerDescription
'o'Circle
'+'Plus sign
'*'Asterisk
'.'Point
'x'Cross
'_'Horizontal line
'|'Vertical line
's'Square
'd'Diamond
'^'Upward-pointing triangle
'v'Downward-pointing triangle
'>'Right-pointing triangle
'<'Left-pointing triangle
'p'Pentagram
'h'Hexagram
ColorDescription

y

yellow

m

magenta

c

cyan

r

red

g

green

b

blue

w

white

k

black

Target axes, specified as an Axes object.

Extended Capabilities

See Also

Functions

Properties

Introduced before R2006a