MATLAB Programming/Graphics

2D Graphics

Plot

Plots a function in Cartesian Coordinates, x and y.
Example:

x=0:0.1:2;  % creates a line vector from 0 to 2
fx=(x+2)./x.^2; % creates fx
plot(x,fx,'-ok') % plots 2d graphics of the function fx 

To plot 2 or more graphs in one Figure, then simply append the second (x,y) pair to the first:

>>>x1 = [1,2,3,4]
>>>y1 = [1,2,3,4]
>>>y2 = [4,3,2,1]
>>>plot(x1,y1,x1,y2)

This will plot y1 and y2 on the same x-axis in the output.

Polar Plot

Plots a function using θ and r(θ)

t = 0:.01:2*pi;
polar(t,sin(2*t).^2) 

3D Graphics

plot3

The "plot3" command is very helpful and easy to see three dimensional images. It follows the same syntax as the "plot" command. If you search the MATlab help (not at the command prompt. Go to the HELP tab at the top of the main bar then type plot3 in the search) you will find all the instruction you need.

Example:

l=[-98.0556  ; 1187.074];       
f=[ -33.5448 ; -240.402];       
d=[ 1298     ; 1305.5]           
plot3(l,f,d); grid on;

This example plots a line in 3d. I created this code in an M-file. If you do the same you change the values and hit the run button in the menu bar to see the effect.

Mesh

Creates a 3D plot using vectors x and y, and a matrix z. If x is n elements long, and y is m elements long, z must be an m by n matrix.

Example:

x=[0:pi/90:2*pi]';
y=x';
z=sin(x*y);
mesh(x,y,z);

Contour

Creates a 2D plot of a 3D projection, using vectors x and y, and a matrix z. If x is n elements long, and y is m elements long, z must be an m by n matrix.

Example:

x=[0:pi/90:2*pi]';
y=x';
z=sin(x*y);
contour(x,y,z);

Contourf

Same as contour, but fills color between contour lines

Surface

Basically the same as mesh