=

does not mean equality

adding to a variable

ex. mynum= mynum+1 increments by 1

subtracting from a variable

ex. num = num-1 decrements by 1

ex. variable names

rules:

must begin with letter

can have letters, digits, and _ (underscore)

no spaces

limit to length (namelengthmax to find)

case-sensitive (Num_1 =/= num_1)

cannot be a reserved word

*should* not be name of built-in function

shows variables that have been defined in this Command Window (only shows variable names)

>>who

Your variables are:

ans mynum variablename

shows more information on variables defined in Command Window

shows name, size, bytes, class, attributes

default

4 decimal places

default

ans=

     128

ans=

   128

...

used for long expressions that continue on the next line

ex.

3 + 5 - 62 + 4 - 5 ...

+ 22 - 1

ans=

16

operates on a single value

ex.

"-"

-7

negative

value that an operator operates on

ex.

7 and 2 in

7*2

operates on 2 values

ex.

+

-

*

/ divided by

\ divided into

^ exponentiation

priority in order of operations

 parenthesis can change precedence

highest->lowest precedence:

()

^

- (negation)

*, /, \

+, -

inner parentheses evaluated first

ex.

3*((4^2)+7)

lists and describes built-in elementary functions

broken into trigonometric (for which the default is radians), exponential, complex, and rounding
and remainder functions

value that function is applied to

ex.

abs(-4)

calls the function abs

returns 4

returns either 1 or -1 or 0

indicates positive, negative or 0

matlab stores

pi   3.14...

i   sqrt(1)

j   sqrt(1)

inf   infinity

NaN   (0/0)

e is not stored as constant

e=exp(1)

=2.7183

default

for "double precision"

larger numbers than single

int8 - 8 bits to store the integer and its sign (-128 to 127)

int16

int32

int64

to find the range for each, use intmin('int32') and intmax('int32')

using the smallest type saves space

if you go beyond the range of a type, it will use its max instead

int8(200) = 127

stores single characters (eg 'x')

or

strings, sequences of characters (eg 'cat')

enclosed in ' '

changing a value to a different type

use name of type changed to as fuction

ex.

change num from double to int32

num=int32(num)

pseudo-random, start with seed that is predetermined or assigned by a clock in the computer

the seed is the same every time Matlab is opened, unless that state is changed

rand('state',sum(100*clock))

generates a random number between 0 and 1

with 4 decimal places

>>rand

ans=

.2311

rand*n will generate a random number from 0 to n

rand*7

to generate a random number from low to high

low=4;

high=5;

rand*(high-low)+low

>> randint(1,1,n)
generates one random integer in the range from 0 to n-1

(default type double)

>> randint(1,1,[1,20])

generates a random integer between 1 and 20

 includes all letters of the alphabet, digits, punctuation marks, and more; all the keys on a keyboard

given integer values

use ' ' for characters

 American Standard Code for Information Interchange

128 characters

integer values from 0 to 127

converts from number type to char type

ex.

char(97)

ans=

a

sequence of characters

ex.

'abcd'

double('abcd')

ans=

97  98  99  100

char('abcd'+1)

ans=

bcde

dimensions r x c (r by c)

2d array

mat=[1 2 3; 4 5 6]

or

mat=[1:3; 4:6]

rand(r) creates a rxr matrix of random values between  0 and 1

rand(r,c) creates a r x c matrix of random numbers between 0 and 1

>> randint(2,4,[10,30]) creates a 2x4 matrix with random values in [10, 30]

zeroes(r,c) creates an r x c matrix of zeroes

1xn or nx1

row or column vector

row: v=[1 2 3 4] or v=[1,2,3,4] or v=1:5

 column: v' or [1;2;3;4]

subset of matrix

one dimensional array

1x1

subset of matrix

first:step:last

nv=1:2:9

nv=

1    3    5    7    9

nv=1:-2:9

9    7    5    3    1

:

1:5

1 2 3 4 5

x:y

iterates through x to y

regularly spaced

linspace(x,y,n) creates a vector with n values in the inclusive range [x,y], evenly (linearly) spaced

linspace(3,15,5)

3    6    9    12    15

combine two vectors

vec1 = 1:2:9=[1    3    5    7    9]

vec2 = linspace(3,15,5)=[3    6    9    12    15]

newvec = [vec1 vec2]

newvec=

1    3    5    7    9    3    6    9    12    15

aka subscript

element number

indexes start at 1 in MATLAB

vec=[3   12    7    1]

vec(2)=12

also a vector

vec=[3   12   7   1]

vec(2:4)= [12   7   1]

uses colon operator :

used to get specified elements of another vector

index=[1   3    4]

vec=[ 2   6    7    3    9]

vec(index)=vec([1   3   4])=

[2   7   3]

vec=[ 2   6    7    3    9]

assign vec(7)=12

vec=

[ 2   6    7    3    9    0    12]

inserts 0 for unassigned elements

mat(2,3) calls the element in the 2nd row and 3rd column

mat =
2    3    4
3    4    5

>> mat(1:2,2:3) 1st and 2nd row, 2nd and 3rd column
ans =
3    4
4    5

: means all rows or all columns

mat(:,:)=mat

mat(2,:) - 2nd row, all columns

mat(:,3) - all rows, 3rd column

when single index is used, unwinds by columns

ex.

mat =
2    3    4
3    4    5

mat(4)= 4

replace 2nd row

mat(2,:)=5:7

replace 3rd column

mat(:,3)=[3 4]'

must have correct number of elements!

mat(4,:)=2:2:8

mat =
2    11    4    9
5     6    7    2
0     0    0    0
2     4    6    8

adds 0's to unassigned elements

gives dimensions of an array

vec=[-2 1 0 1]

size(vec)=

1 4

1x4

r x c

refers to the last column or row

mat(end, 1) calls the element in the last row, first column

changes the dimensions of a matrix

iterates through the matrix columnwise

flips matrix from left to right

first column becomes last column etc

flips up to down

first row becomes last row etc

rotates the matrix clockwise 90 degrees

top-right corner becomes top-left corner

repmat(mat,m,n)

creates a larger matrix which consists of an m x n matrix copies of mat

[ ]

can be used to delete elements or subsets from vectors

vec=1:5

vec(3)=[]

vec=

1  2  4  5

Confusing the two division operators / and \