Introduction to Matlab (Code)
intro.m
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% Introduction to Matlab
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% (1) Basics
% The symbol "%" is used to indicate a comment (for the remainder of
% the line).
% When writing a long Matlab statement that becomes to long for a
% single line use ".
.." at the end of the line to continue on the next
% line.
E.g.
A = [1, 2;
...
3, 4];
% A semicolon at the end of a statement means that Matlab will not
% display the result of the evaluated statement. If the ";" is omitted
% then Matlab will display the result.
This is also useful for
% printing the value of variables, e.g.
A
% Matlab's command line is a little like a standard shell:
%  Use the up arrow to recall commands without retyping them (and
%
down arrow to go forward in the command history).
%  Ca moves to beginning of line (Ce for end), Cf moves forward a
%
character and Cb moves back (equivalent to the left and right
%
arrow keys), Cd deletes a character, Ck deletes the rest of the
%
line to the right of the cursor, Cp goes back through the
%
command history and Cn goes forward (equivalent to up and down
%
arrows), Tab tries to complete a command.
% Simple debugging:
% If the command "dbstop if error" is issued before running a script
% or a function that causes a runtime error, the execution will stop
% at the point where the error occurred. Very useful for tracking down
% errors.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% (2) Basic types in Matlab
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% (A) The basic types in Matlab are scalars (usually doubleprecision
% floating point), vectors, and matrices:
A = [1 2; 3 4];
% Creates a 2x2 matrix
B = [1,2; 3,4];
% The simplest way to create a matrix is
% to list its entries in square brackets.
% The ";" symbol separates rows;
% the (optional) "," separates columns.
N = 5
% A scalar
v = [1 0 0]
% A row vector
v = [1; 2; 3]
% A column vector
v = v'
% Transpose a vector (row to column or
%
column to row)
v = 1:.5:3
% A vector filled in a specified range:
v = pi*[4:4]/4
%
[start:stepsize:end]
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(brackets are optional)
v = []
% Empty vector
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% (B) Creating special matrices: 1ST parameter is ROWS,
%
2ND parameter is COLS
m = zeros(2, 3)
% Creates a 2x3 matrix of zeros
v = ones(1, 3)
% Creates a 1x3 matrix (row vector) of ones
m = eye(3)
% Identity matrix (3x3)
v = rand(3, 1)
% Randomly filled 3x1 matrix (column
% vector); see also randn
% But watch out:
m = zeros(3)
% Creates a 3x3 matrix (!) of zeros
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% (C) Indexing vectors and matrices.
% Warning: Indices always start at 1 and *NOT* at 0!
v = [1 2 3];
v(3)
% Access a vector element
m = [1 2 3 4; 5 7 8 8; 9 10 11 12; 13 14 15 16]
m(1, 3)
% Access a matrix element
%
matrix(ROW #, COLUMN #)
m(2, :)
% Access a whole matrix row (2nd row)
m(:, 1)
% Access a whole matrix column (1st column)
m(1, 1:3)
% Access elements 1 through 3 of the 1st row
m(2:3, 2)
% Access elements 2 through 3 of the
%
2nd column
m(2:
end
, 3)
% Keyword "end" accesses the remainder of a
%
column or row
m = [1 2 3; 4 5 6]
size(m)
% Returns the size of a matrix
size(m, 1)
% Number of rows
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 Spring '10
 mustafa
 Linear Algebra, Column vector, Stefan Roth

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