Matlab Basics

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The Command Window

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Defining Variables

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Useful Commands

Command Description Example (try these out)
who Lists variables currently defined in MATLAB.
a = 5; b = 6; c = linspace(0,50,10);
who
whos Similar to who, but gives additional information.
a = 5; b = 6; c = linspace(0,50,10);
whos
clear Clear all variables defined.
a = 5; b = 6; c = linspace(0,50,10);
clear;            % clears all variables
who;              % displays nothing - no variables defined.
a=2; b=5; c=a+b;
clear a b;        % only clears a and b.  c is still here.
who;              % tells us that c is defined.
clc Clears the MATLAB workspace. Doesn't clear variables
clc
save saves variables to a file that can be loaded later.
clear;
a=5; b=6; c=a+b*2;
save myVariables;  % saves all variables to the file "myVariables.mat"
save bcVars b c;   % saves b and c only to "bcVars.mat"
load loads variables from a file
clear;
a=5; b=6; c=a+b*2;
save myVariables;
save bcVars b c;
clear;
load bcVars;       % b and c are now defined.
who;
clear;
load myVariables;  % a b and c are all defined.
who;
help provides help on how to use a command
help clear;
help load;
help save;

Basic Operations

MATLAB supports basic operations

Basic Operators
Operator Description Examples
+ Addition
1 + 2            % displays 3
b = 1+2;         % assigns 3 to the variable b.
a = cos(pi)+2.0; % a=1
- Subtraction
1 - 2               % displays -1
b = 1-2;            % assigns -1 to the variable b.
a = sqrt(-4*b)+2.0; % a=4
* Multiplication
2.2*3.3       % displays 6.6
a = 2.2*3.3;  % assigns 6.6 to a.
b = (pi/4);   % assigns sqrt(2)/2 to b.
/ Division
6.6/2.2       % dispays 3.3
a = 6.6/2.2;  % assigns 3.3 to a.
b = sqrt(a/pi)*exp(a);
^ Power
2^3                 % displays 8
a = 2^3 + 243^0.2;  % assigns 11 to a.
( ) Parentheses
a = (2+5)*3;  % assigns 21 to a
b = 2+5*3;    % assigns 17 to b
c = 2*(a-10); % assigns 22 to c

NOTE: if you are using arrays, then the / and * operators have different behavior! See the page on array arithmetic for more information.


In addition, MATLAB has many built-in functions. Type help elfun at the MATLAB command prompt for a list. Some commonly used functions are given here:

Function Description
cos The cosine function
sin The sine function
tan The tangent function
sqrt The square-root, \sqrt(x)=x^{1/2}
exp The exponential function
log10 The base-10 log function, \log(10^x)=x
log The natural log function, \ln(\exp(x))=x
abs The absolute value, \left|x\right|


M-Files

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An M-file is a series of MATLAB commands that you save in a file. Then you can re-run them easily and make changes without re-entering everything again. Anything that can be done in the command window can also be done from an m-file.

MATLAB's Path

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