﻿ ﻿Syntax: Quick Reference - Essential MATLAB for Engineers and Scientists (2013)

# Essential MATLAB for Engineers and Scientists (2013)

### Syntax: Quick Reference

In this appendix we offer examples of the MATLAB syntax most commonly used in this book.

A.1. Expressions

x = 2 ^ (2 * 3) / 4;

x = A \ b; % solution of linear equations

a == 0 & b < 0 % a equals 0 AND b less than 0

a ~= 4 | b > 0 % a not equal to 4 OR b greater than 0

A.2. Function M-files

function y=f(x) % save as f.m

% comment for help

function [out1, out2] = plonk(in1, in2, in3) % save as plonk.m

% Three input arguments, two outputs

...

function junk % no input/output arguments; save as junk.m

[t, x] = ode45(@lorenz, [0 10], x0); % function handle with @

A.3. Graphics

plot(x, y), grid % plots vector y against vector x on a grid

plot(x, y, 'b--') % plots a blue dashed line

plot(x, y, 'go') % plots green circles

plot(y) % if y is a vector plots elements against row numbers

% if y is a matrix, plots columns against row numbers

plot(x1, y1, x2, y2) % plots y1 against x1 and

y2 against x2 on same graph

semilogy(x, y) % uses a log10 scale for y

polar(theta, r) % generates a polar plot

A.4. if and switch

if condition

statement % executed if condition true

end;

if condition

statement1 % executed if condition true

else

statement2 % executed if condition false

end;

if a == 0 % test for equality

x = -c / b;

else

x = -b / (2*a);

end;

if condition1 % jumps off ladder at first true condition

statement1

elseif condition2 % elseif one word!

statement2

elseif condition3

statement3

...

else

statementE

end;

if condition statement1, else statement2, end % command line

switch lower(expr) % expr is string or scalar

case {'linear','bilinear'}

disp('Method is linear')

case 'cubic'

disp('Method is cubic')

case 'nearest'

disp('Method is nearest')

otherwise

disp('Unknown method.')

end

A.5. for and while

for i = 1:n % repeats statements n times

statements

end;

for i = 1:3:8 % i takes values 1, 4, 7

...

end;

for i = 5:-2:0 % i takes values 5, 3, 1

...

end;

for i = v % index i takes on each element of vector v

statements

end;

for v = a % index v takes on each column of matrix a

statements

end;

for i = 1:n, statements, end % command line version

try,

statements,

catch,

statements,

end

while condition % repeats statements while condition is true

statements

end;

while condition statements, end % command line version

A.6. Input/output

disp( x )

disp( 'Hello there' )

disp([a b]) % two scalars on one line

disp([x' y']) % two columns (vectors x and y

must be same length)

disp( ['The answer is ', num2str(x)] )

fprintf( '\n' ) % new line

fprintf( '%5.1f\n', 1.23 ) % **1.2

fprintf( '%12.2e\n', 0.123 ) % ***1.23e-001

fprintf( '%4.0f and %7.2f\n', 12.34, -5.6789 )

% **12 and **-5.68

fprintf( 'Answers are: %g %g\n', x, y )

% matlab decides on format

fprintf( '%10s\n', str ) % left-justified string

x = input( 'Enter value of x: ' )

name = input( 'Enter your name without apostrophes: ', 's' )

load filename % retrieves all variables

from binary file filename.mat

load x.dat % imports matrix x from ASCII file x.dat

save filename x y z % saves x y and z in filename.mat

save % saves all workspace variables

in matlab.mat

save filename x /ascii % saves x in filename (as ASCII file)

A.8. Vectors and matrices

a(3,:) % third row

a(:,2) % second column

v(1:2:9) % every second element from 1 to 9

v([2 4 5]) = [ ] % removes second, fourth and fifth elements

v(logical([0 1 0 1 0])) % second and fourth elements only

v' % transpose

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