=================
=== 2D graphs ===
=================

==============================
=== simple graphs (ez...) ====
==============================

ezplot('x*sin(x)')  % on interval < -2*pi, 2*pi >

   or:

f = 'x*sin(x)';
ezplot(f)

ezplot(f, [-2, 10])   % on interval < -2, 10 >
% or ezplot(f, -2, 10) 

grid on
grid off


=======  for 2 variables ============

ezplot('x^2 + y^2 - 4')

ezsurf('x^2 + y^2 - 4')
colorbar
ezmesh('x^2 + y^2 - 4')
ezcontour('x^2 + y^2 - 4')

f = 'x^2 - y^2-5';
ezplot(f, [-10, 10])        % in a square
ezplot(f, [-10, 10, -5, 5]) % in a rectangle


-----  graphical solution of equations ---

ezplot('x^2 + 1')        % the first function
hold on                  % next plot to the same figure
ezplot('x^2 + y^2 - 4')  % the second function
hold off                 % next plot wipe away the previous one

axis([-2 2 0 3])         % zoom in

or:
   xlim([-1.5 , 1.5])   % interval on x axis
   ylim([1.5 , 2])      % interval on y axis

axis equal


ezsurf('x^2 + y^2 - 4')
hold on                  
ezsurf('-x^2 + y + 8')


=============================
==== command plot ===========
=============================

x = -pi:0.3:pi;   % points on x axis (from -pi to pi, step 0.3)
y = x.*sin(x);    % points on y axis (function values)

plot(x, y)                      % points connected by blue lines
plot(x,y, 'r')                  % red line
plot(x,y, 'r', 'linewidth', 2)  % thicker red line
plot(x,y, 'r*')                 % points marked as red asterisks
plot(x,y, 'k--o', 'linewidth', 2)  % dashed black line, circles
hold on
plot(x,y, 'mo', 'linewidth', 6) % bigger magenta circles
hold off

xlabel('x: (-pi, pi)')
ylabel('x*sin(x)')
title('Plot of the function  x*sin(x)')


help plot   % other possibilities


--- more functions in one graph ---

x = pi*[-1:0.1:1]; 
y1 = sin(x);  
y2 = cos(x).^2; 
y3 = exp(x);

plot(x, y1, x, y2, 'r', x, y3, 'k')

legend('sin(x)','cos(x)^2', 'e^x')
legend('sin(x)','cos(x)^2', 'e^x', 'location', 'northwest')
     

   --- or :

plot(x, [y1; y2; y3])   % rows of 2. matrix
plot(x, [y1' y2' y3'])  % columns of 2. matrix

   --- or one after another ---

plot(x, y1)
hold on       % continue on the same picture
plot(x, y2)
plot(x, y3)
hold off      % next time opens a new picture


------- more plots in one picture ----

subplot(3,1,1); plot(x,y1)  % division 3 rows, 1 columns, 1-st picture
subplot(3,1,2); plot(x,y2)
subplot(3,1,3); plot(x,y3)

   --- managing more pictures ---

f1 = figure;   % 1. picture
f2 = figure;   % 2. picture
f3 = figure;   % 3. picture prints to actual (i.e. 3.) picture
figure(f1);    % switch to 1. pict.
plot(x, y1)    % draws to 1. pict.
figure(f2);    % switch to  2. pict.
plot(x, y2)    % draws to 2. pict.

close(f2)  % close 2. pict.
close all  % close all pict.


--- parametric curve ---

t = 0 : 0.2 : 2*pi;
x = sin(t);
y = cos(t);	
plot(x, y)

axis equal
axis normal


===========================
======= 3D graphs ==========
===========================

t = 0 : pi/50 : 10* pi;
plot3(sin(t), cos(t), t, 'r*')
zlabel('z')

============ graph on a rectangle mesh ================

 x = 0 : 0.3 : 10;         % mesh on x axis
 y = -5 : 0.2 :5;          % mesh on y axis
 [xx,yy] = meshgrid(x,y);  % rectangular mesh on xy plane
 z = xx.^2 + yy.^3;        % computation of the z-coordinate at mesh nodes

 mesh(xx,yy,z)    % mesh graph
 colorbar         
 meshc(xx,yy,z)   % mesh graph with isolines (contours) in xy plane
 surf(xx,yy,z)    % surface graph
 surfc(xx,yy,z)   % surface graph with isolines


============ graph on an irregular mesh ================

 n = 50;                % number of points (nodes)
 x = rand(1,n);         % coordinates of nodes (here random numbers)
 y = rand(1,n);
 z = y + sin(3*x);      % function values at nodes
 tri = delaunay(x,y);   % triangulation 
 trisurf(tri, x, y, z)  % surface graph
 trimesh(tri, x, y, z)  % mesh graph

=======================================================