Useful Links

- www.mathworks.com
- MatLab tutorials from mathworks
- MatLab 7 Getting Started Guide
- Neural Network Toolbox from mathworks
- Neural Network Toolbox 6 User's Guide

Let's Start

Hey, you know how to install and run MatLab right? Let's skip this part. If you do not know, you can google it. It is too easy.

I use the MatLab 7 Getting Started Guide, which is free (really and legally) from the mathworks website.

Examples

Check out the

Chapter 1. Product Overview

Do I look like a salesman? Let's skip this part.

Chapter 2. Matrices and Arrays

Enter matrices into MATLAB in several different ways

- Enter an explicit list of elements.
- Load matrices from external data files
- Generate matrices using built-in functions.
- Create matrices with your own functions in M-files

**
Enter maxtrix** as a list of elements:

*A = [16 3 2 13; 5 10 11 8; 9 6 7 12; 4 15 14 1]*

Use a semicolon, ; , to indicate the end of each row. It is automatically remembered in the MATLAB workspace

sum, transpose, and diag

*sum(A)* => sum of all columns

*A' *=> transpose

*diag(A)* => main diagonal

*fliplr(A)* => flips a matrix from left to right

Subscripts

The element in row i and column j of A is denoted by A(i,j).

*A(1,4) + A(2,4) + A(3,4) + A(4,4)*

It is also possible to refer to the elements of a matrix with a single subscript, A(k). A(8) is another way of referring to the value 15 stored in A(4,2). Conversely, if you store a value in an element outside of the matrix, the size increases to accommodate the newcomer:

The Colon Operator

*1:10* => row vector containing the integers from 1 to 10:

*1 2 3 4 5 6 7 8 9 10*

*100:-7:50* => nonunit spacing

*100 93 86 79 72 65 58 51*

*0:pi/4:pi
0 0.7854 1.5708 2.3562 3.1416*

*A(1:k,j)* => first k elements of the jth column of A. Thus:

* sum(A(1:4,4))*

The colon by itself refers to all the elements in a row or column of a matrix and the keyword end refers to the last row or column.

*sum(A(:,end))* => computes the sum of the elements in the last column of A

sum(1:16)

The magic Function

creates magic squares of almost any size: *magic(4)*

Expressions

These expressions involve entire matrices.

Variables

*num_students = 25 *=> creates a 1-by-1 matrix

Variable names consist of a letter, followed by any number of letters, digits, or underscores. MATLAB is **case sensitive**; it distinguishes between uppercase and lowercase letters. MATLAB uses only the first N characters of the name, (where N is the number returned by the function *namelengthmax*), and ignores the rest.

Numbers

*3
-99
0.0001
9.6397238
1.60210e-20
6.02252e23
1i
-3.14159j
3e5i*

Imaginary numbers (complex number whose squared value is a real number not greater than zero, i think here only means complex number) use either i or j as a suffix.

*sort([3+4i, 4+3i])
angle(3+4i)*

Operators

+ Addition

- Subtraction

* Multiplication

/ Division

\ Left division (described in “Linear Algebra” in the MATLAB documentation)

^ Power

' Complex conjugate transpose

( ) Specify evaluation order

Functions

e.g.* abs, sqrt, exp, and sin.
help elfun* => elementaty maths functions

*pi* 3.14159265...

*i *Imaginary unit,

*j* Same as i

*eps* Floating-point relative precision,

*realmin* Smallest floating-point number,

*realmax* Largest floating-point number,

*Inf *Infinity

*NaN* Not-a-number

Generating Matrices

*zeros* All zeros

*ones* All ones

*rand* Uniformly distributed random elements

*randn* Normally distributed random elements

*zeros(2,4)*

*ones(3,3)*

*rand(1,10)
fix(10*rand(1,10))*

*randn(4,4)*

**
The load Function** - Load content from file

The load function reads binary files containing matrices generated by earlier MATLAB sessions, or reads text files containing numeric data. The text file should be organized as a rectangular table of numbers, separated by blanks, with one row per line, and an equal number of elements in each row.

Steps:

- outside of MATLAB, create a text file containing these four lines (for a matrix):

*16.0 3.0 2.0 13.0*

5.0 10.0 11.0 8.0

9.0 6.0 7.0 12.0

4.0 15.0 14.0 1.0 - Save the file as magik.dat in the current directory.
- The statement

load magik.dat

reads the file and creates a variable, magik, containing the example matrix.

**The save Function** - Save workspace variables to disk.

SAVE FILENAME X - save variable X to filename

*save test.txt magik -ASCII* - save variable magik to filename text.txt with ASCII option

ASCII Options:

SAVE ... -ASCII uses 8-digit ASCII form instead of binary regardless

of file extension.

SAVE ... -ASCII -DOUBLE uses 16-digit ASCII form.

SAVE ... -ASCII -TABS delimits with tabs.

SAVE ... -ASCII -DOUBLE -TABS 16-digit, tab delimited.

**Deleting rows and Columns**

Then, to delete the second column of X, use

X(:,2) = []