% 1. basic plotting
% we always separate the computation of the samples
% from the actual rendering, done by plot
x = -pi:0.01:pi;
y = sin(x); 
plot(x,y)
axes([-pi,pi,-1,1])
??? Error using ==> axes
Invalid object handle.

axis([-pi,pi,-1,1])
hold on 
plot(x,y,'r+')
% with hold on the plot in the window stays
% we can mark the samples with red crosses
hold off
x = 0:pi

x =

     0     1     2     3

c = cos(x);
plot(x,c)
x = 0:0.5:pi

x =

  Columns 1 through 5

         0    0.5000    1.0000    1.5000    2.0000

  Columns 6 through 7

    2.5000    3.0000

c = cos(x);
plot(x,c)
x = 0:0.1:2*pi;
c = cos(x);
plot(x,c)
axis([0,2*pi,-2,2])
hold on
plot(x,c,'gx')
figure
% 2. polar plots
t = 0:0.1:10*pi;
r = 0.01*t.^2 -0.02;
% Observe the dot . before the hat ^ !
% Dotwise operations mean that we execute
% it componentwise.
polar(t,r)
% 3. three dimensional plots
% For surfaces, we must first define a grid.
% For plotting cos(x*y), for x in [-2,2] and
% y also in [-2,2], we first need to make a grid.
xa = -2:0.2:+2; ya = -2:0.2:+2;
[x,y] = meshgrid(xa,ya);
z = cos(x .* y); % observe the dot before * !!!
figure
mesh(x,y,z)
view(3)
view(3)
view([-16,5])
% Special Three dimensional plots
% with plot3 we draw space curves
t = 0:0.1:10*pi;
figure
x = cos(3*t); y = sin(3*t); z = t;
plot3(x,y,z)
% subplots
% we can choose a different window for every plot
% or create several plots in the same window
figure
subplot(2,2,1)
plot3(x,y,z)
subplot(2,2,2)
plot3(x,y,z)
subplot(2,2,3)
plot3(x,y,z)
subplot(2,2,4)
plot3(x,y,z)
% contour plots
r = -2:.1:2;
[x,y] = meshgrid(r,r);
z = x.*exp(-x.^2 - y.^2);
figure
subplot(2,1,1)
mesh(x,y,z)
subplot(2,1,2)
contour(z)
contour(z,20)
subplot(2,1,1) % make first subplot active again
view(3) % restore the default view
diary off