Modeling and Simulation Lecture Notes: Introduction to Matlab and 2D Plotting, Slides of Mathematical Modeling and Simulation

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Lecture Slides

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Modeling and Simulation

Lecture: Introduction to Matlab

Creating a 2D Plot

x = 0:pi/100:2pi; y = sin(x); plot(x,y,'LineWidth',3)*

Now label the axes and add a title. The characters \pi create the symbol. See text strings for more symbols: xlabel('x = 0:2\pi') ylabel('Sine of x') title('Plot of the Sine Function','FontSize',12)

For example, these statements use the colon operator to create a vector of x values ranging from 0 to 2, compute the sine of these values, and plot the result:

Graph is on

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Plotting Elementary Functions

% prog2.m t = -1 : 0.01 : 1; f = 4.5cos(2pit - pi/6); plot(t,f 'LineWidth',3),title('Fig.2a'); axis([-1, 1, -6, 6]); xlabel('time, t'); ylabel('f(t)'); text(-0.6, 5,' f(t) = A cos(wt + phi)'); grid;*

Example of a graph ploting with labels and text and grid.

Graph is on

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Plotting Elementary Functions

Resulting graph

Specifying the Color and Size of Markers

Resulting

figure

Plotting commands

PLOT(X,Y) plots vector Y versus vector X. TITLE('text') adds text at the top of the current plot. XLABEL('text') adds text beside the X-axis on the current axis. YLABEL('text') adds text beside the Y-axis on the current axis. GRID, by itself, toggles the major grid lines of the current axes.

GTEXT('string') displays the graph window, puts up a cross-hair, and waits for a mouse button or keyboard key to be pressed. SUBPLOT(m,n,p), or SUBPLOT(mnp),

breaks the Figure window into an m-by-n matrix of small axes. STEM(Y) stemDiscrete sequence or "stem" plot. STEM(Y) plots the data sequence Y as stems from the x axis terminated with circles for the data value. SEMILOGX(...) is the same as PLOT(...), except a logarithmic (base 10) scale is used for the X-axis. SEMILOGY(...) is the same as PLOT(...), except a logarithmic (base 10) scale is used for the Y-axis..

Results

Multiple Graphs

Plotting colors and line styles

Colors Line Styles y yellow. point M magenta o circle C cyan x x-mark R red + plus G green - solid B blue * star W white : dotted K black -. Dashdot -- dashed More mark types are; square(s), diamond(d), up-triangle(v), down- triangle(^), left-triangle(<), right-triangle(>), pentagram(p), hexagram(h) See also help plot for more line and mark color.

Results

subplots

Various Plotting Functions:

 2 dimensions line plots (x vs. y),  filled plots,  bar charts,  pie charts,  parametric plots,  polar plots,  contour plots,  density plots,  log axis plots,  surface plots,  parametric plots in 3 dimensions  and spherical plots.

To preview some of these capabilities and others as well, enter the command demos.

MATLAB supports many types of graph and surface plots:

Line Plots of 3-D Data

Production of helix

3-D Plots

MATLAB Commands for Mesh and Surface

meshgrid: generate X and Y arrays for 3-D plots mesh: draws a wireframe mesh surf: plot a 3-D shaded surface colorbar: add a color bar tool patch: creating patch graphics objects hidden: remove hidden lines from mesh plot

Mesh and Surface (Example) (2)

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Z = sin(R)./R; mesh(X,Y,Z) 1

Three-D meshgrid

Mesh and Surface

Three-D meshgrid