Plotting - Advanced

FPLOT

Plots a function f(x) written as a string within quotation marks. The free variable needs to be designated with x.

The lower and upper limits for x are given as a row vector with two values, as the second argument of the function.

Example:fplot('x.*sin(x)', [0 10*pi])

FPLOT example

Example of fplot: fplot('x.*sin(x)', [0 10*pi])

Logarithmic plotting

Many functions tend to increase exponentially after some point. This presents problems in viewing the behavior (or see the values) of the function where it is close to zero.

To accentuate low values and compress the high ones, the axis where the values get too high are plotted on a logarithmic scale.

In MATLAB, we can plot x-axis, y-axis, or both axes on a logarithmic scale.

Chart type: SEMILOGX

Example:x= e-t, y= t, 0≤t≤2

t= linspace(0, 2*pi, 200);x= exp(-t); y= t;plot(x,y); grid;

t= linspace(0, 2*pi, 200);x= exp(-t); y= t;semilogx(x,y); grid;

Chart type: SEMILOGY

Example:y= e-x2, -3 ≤ x ≤ 3

x= linspace(-3, 3, 101);y= exp(-x.^2);plot(x,y); grid;

x= linspace(-3, 3, 101);y= exp(-x.^2);semilogy(x,y); grid;

Chart type: LOGLOG

Example:x= e-t, y= 100 + e2t, 0 ≤ t ≤ 2

t= linspace(0, 2*pi, 200);x= exp(-t); y= 100+exp(2*t);plot(x,y); grid;

t= linspace(0, 2*pi, 200);x= exp(-t); y= 100+exp(2*t);loglog(x,y); grid;

Chart type: POLAR

Plots a radial function around 360° Example:

r2= 2 sin 5t, 0 ≤ t ≤ 2

t= linspace(0, 2*pi, 200);r= sqrt(abs(2*sin(5*t)));polar(t,r);

Chart type: FILL

Example:r2= 2 sin 5t, 0 ≤ t ≤ 2x= r cos t, y= r sin t

t= linspace(0, 2*pi, 200);r= sqrt(abs(2*sin(5*t)));x= r.*cos(t); y= r.*sin(t);fill(x,y,'r'); axis('square');

Chart type: BAR

Example:r2= 2 sin 5t, 0 ≤ t ≤ 2y= r sin t

t= linspace(0, 2*pi, 200);r= sqrt(abs(2*sin(5*t)));y= r.*sin(t);bar(t,y); axis([0 pi 0 inf]);

Chart type: BARH

Example: World population by continents

cont= char('Asia', 'Europe', 'Africa', 'N.America', 'S.America');pop=[3332; 696; 694; 437; 307];barh(pop);for i=1:5 gtext(cont(i,:));endxlabel('Population in millions');title('World population 1992');

Chart type: PIE

Example: World population by continents

cont= char('Asia', 'Europe', 'Africa', 'N.America', 'S.America');pop=[3332; 696; 694; 437; 307];pie(pop);for i=1:5 gtext(cont(i,:));endtitle('World population 1992');

Chart type: COMET

Animated linear plot. Example: b= a sin a, 0 ≤ a ≤ 10

a= linspace(0, 10*pi, 2000); b= a.*sin(a); pause(2); comet(a, b);

Multiple charts in a window

Multiple plots may be placed in a window using the SUBPLOT command.

Syntax:subplot(rows, columns, active)

Any plotting command acts on the active subplot only.

Active plot is selected in row-major order.

1 2 3

4 5 6

Multiple charts in a window

Example:

x= linspace(0, 4*pi, 100); subplot(3,2,1); plot(x, sin(x));subplot(3,2,2); plot(2*x, sin(2*x));subplot(3,2,3); plot(x, cos(x));subplot(3,2,4); plot(2*x, cos(2*x));subplot(3,2,5); plot(x, tan(x));subplot(3,2,6); plot(2*x, tan(2*x));