Octave Syntax _octave

Vector

Semicolon: Split Line

Spaces or commas: Split columns Create and access row vectors

Space or comma split

>> v = [1 2 3]% equivalent: v = [1, 2, 3]
v =

   1 2 3
   
>> V (2)% only one row, so specify is the column
ans =  2

Column vectors

Semicolon Split

>> v = [1; 2; 3]
v =

   1
   2
   3

>> V (2)% only one column, so the designation is line
ans =  2

Matrix

Like a vector, a space or comma splits a column, a semicolon splits a row

Colon: represents all, all rows, or all columns created

>>   A = [1, 2; 3, 4]% write
a = 1 2 3 4

>> a = [1, 2;% Branch Write
> 3, 4]< C22/>a =

   1   2
   3   4

Creating tips

A:C---from A to C

A:B:C---from a, interval B, to C

Vectors can also be created in such a way that

>> a = [1:3; 4:6]
a =

   1   2   3
   4   5   6
   
>> a = [1:2:5; 2:2:6]
a =
  1   3   5
   2   4   6

Special matrix Unit Matrix

>> Eye (3)% Unit matrix
ans =

diagonal Matrix

   1   0   0
   0

1 0 0 0 1 >> flipud (Eye (3))
ans =

permutation Matrix

   0   0   1
   0   1 0 1 0   0

Transpose matrix

A =

   1   2
   3   4

>> A '
ans =

   1   3   -2 4

Inverse matrix

A =

   1   2
   3   4

>> PINV (a)
ans =

  -2.00000   1.00000
   1.50000  - 0.50000

>> PINV (a) *
ans =

   1.00000   0.00000
  -0.00000   1.00000

All 1 matrices

>> ones (2, 3)
ans =

   1   1   1   1 1 1

All 0 matrices

>> 0*ones (2, 3)
ans =

   0   0 0 0 0 0
>> Zeros (2, 3)
ans =

   0   0   0
   0   0   0

Random matrices

>> rand (1, 3)% 0~1 random number, 1 Rows 3 column
ans =

   0.99291   0.65946   0.95102

Gauss Distribution Matrix

>> Randn (1, 3)% Gauss distribution
ans =

   0.14646   2.02587   1.33266

Access

Colon: represents all, all rows, or all columns access elements

A =

   1   2   3 4 5 6 7 8 9
   
>> A (2, 2)% second row, second column, first set row and then order
ans =  5

Access single or single column

>> A (1,:)% of the first line, all, elements
ans =

   1   2   3
   
>> A (:, 2)% of the second column, all,
ans =

   2
   5< C20/>8

accessing multiple rows or columns

>> A (:, [1, 3])% of the first column and the third column, all, elements
ans =

   1 3 4 6 7 9

>> A ([1, 3],:)% Row and third row, all, elements
ans =

   1   2   3
   7   8   9

Connection

c = [a b], add B by column to a, generate C

C = [A; b], add B by row to a, build C add element

>> a = [1]
a =  1

>> a = [A, 2]% 2, by column, add to a, then assign to a =

   1   2
   
>> a = [A; 3]% A has two columns, 3 has only one column, the scale does not match
error:vertical dimensions mismatch (1x2 vs 1x1)

Add a row or column

>> a = [A; [3, 4]] % the vector [3, 4], as a row, is added to a, which is assigned to a a
=

   1   2
   3   4
   
>> A = [A, [5; 6]]% to the vector [5, 6], as a column, to a, in the assigned to the a< C50/>a =

   1   2   5
   3   4   6

Matrix Connection

>> a = [1, 2; 3, 4]
A = 1 2 3 4

>> B = [5, 6; 7, 8]
B =

   5   6
   7   8
  >> [A; b]% will B, as row, added to a on
ans =

   1   2
   3   4
   5   6 7 8

All the data into a vector

>> a
a =

   1   2
   3   4

>> A (:)
ans =

+ 1 3 2 4 >> A (:) '
ans =

   1   3   2   4

assigning values

On the basis of access, given data of the same size

A =

   1   2   3 4 5 6 7 8 9

>> A (3, 3) = 10 Modify the value of a single element
a =

    1    2    3
    4 5 6 7 8

>> A (1,:) = [0, 0, 0]% modify a row's value
a =< C60/>0    0    0
    4    5    6
    7    8

>> A (2:3, 2:3)
ans =

    5    6
    8

>> A (2:3, 2:3) = [0, 0; 0, 0]% modifies the value of the specified matrix
a =

   0   0 0 4 0 0< C83/>7   0   0

Operation Plus, minus

>> a = [1 1; 1 1]
A = 1 1 1 1

>> b = [2 2; 2 2]
B =

   2

2 2-2 >> A + B
ans =

   3   3
   3   3

>> a-b
ans =

  -1  -1
  -1  -1< C23/>>> A-1
ans =

  0  0
  0  0

Multiply

>> a = [1 2; 3 4]
A = 1 2 3 4

>> b = [5 6; 7 8]
B =

   5   6
   7
  8

>> A * B
ans =

>>-A%-1 *
ans =

  -1  -2
  -3  -4

Point operation

corresponding element operations

Same dimension: multiplication of corresponding elements

Row dimensions are the same: multiply each row of corresponding elements

Same as Levi: multiply the corresponding elements of each column

A. * b = b. * A

In addition to/; The equal dimensions of the square ^;

A =

   1   1
   1   1

b =

   2   3 2 3

>> A. *
ans =

   2   3
   2   3

Same row dimension

A =

   1   1
   1   1

b =

   5   6

>> A. *
ans =   + 5 6 5 6

Same as the levy degree

A =

   1   1
   1   1

b =

   5
   6

>> A. *
ans =   + 5 5 6 6

Point in addition

Matrix times constant, A * 2, except can be, A/2

Conversely, 2 * A is OK, 2/a is no good, want to use 2./A

A =

   1   2
   3   4

>> 1./a
ans =

   1.00000   0.50000
   0.33333   0.25000

Logic

Each element makes a comparison, marking 0 or 1

&GT,!= (or ~=), &&

A =

   1   2
   3   4

>> A > 2
ans =

   0   0   1 1

Bit operations

or | , Function xor

and &

Non ~

XOR or ^ control statements if

i =  1
>> if i = =
1     > Disp (1)
>  ElseIf i = 2
>     disp (2)
>  Else
>     disp (3)
>  End

For

>> for i = 1:3 from 1 to 3
>     disp (i)
> End
 1
 2
 3

While

>> while I <= 3
>     disp (i)
>     i = i + 1
>  end
 1
 2
 3

Break,continue

No difference function with C, C + +, Java

Size: Getting the Matrix dimension

Length: Get maximum dimension

WHO: Variable list

Whos: Variable details

Clear variable Name: Delete specified variable

Clear: Delete all variables

Find: Returns the subscript that matches the conditional element

Log:log to the end of E

Exp:e How many times the party

ABS: Absolute Value

Floor: Rounding Down

Ceil: Rounding up

Sum: Sum

Prop: Quadrature size

Get The Matrix dimension

A =

   1   2
   3   4
   5   6
>> asize = Size (a)
asize =

   3   2
   
>> Size (A, 1)% 3 line
ans =  3

>> Size (A, 2)% 2 column
ans =  2

Length

Get maximum dimension

A =

   1   2
   3   4
   5   6

>> length (a)% output max dimension
ans =  3

W.H.O.

Variable list

>> who% now have where variable Variables in the current
scope:

A          asize      ans        featuresx  W

Whos

Variable details

>> whos% variable details Variables in the current
scope:

   Attr Name           Size                     Bytes  Class
   = = = = =           = =                     =====  =====
        A              3x2  double
        asize          1x2  Double
        ans            1x20  char
        featuresx     27x2                        432  Double
        W              1x10000                  80000  Double Total is

10082 elements using 80516 bytes

Clear

Delete a variable

>> Clear Featuresx >> who Variables in the current
scope:

A      asize  ans    w
>> Clear% clears all variables
>> who% one variable none.

Find

Returns the subscript that conforms to the criteria element

A =

   5   6
   7   8

>> [R, c] = find (A > 6)% meet the requirements: The second line of the first and second
r =

   2
   2

c =

   1
   2

Sum

Sum

>> a = [1, 2; 3, 4]
A = 1 2 3 4

>> sum (a)% equivalent: Sum (A, 1)
ans =

   4   6
   
>> sum (A, 2)
ans =

   3
   7

Prod

Quadrature

>> a
a =

   1   2
   3   4

>> prod (a)% equivalent: Prod (A, 1)
ans =

   3   8

>> prod (A, 2)
ans =

    2
   12

Max Vector

>> a = [1 5 2 3.3]
a =

   1.0000   5.0000   2.0000   3.3000

>> Max (a)
ans =  5

>> [val, Ind] = max (a)
val =  5
ind =  2

Matrix comparison

Two matrices compare each element, keep the large

>> A = rand (3)
A =

   0.2620788   0.6346345   0.4659161
   0.0880455   0.1258945   0.0079559
   0.0296765   0.7917592   0.4321800

>> b = rand (3)
B =

   0.039237   0.672424   0.214649
   0.491320   0.362929   0.197626
   0.821090 0.675265 0.698960

>> Max ( A, B)
ans =

   0.26208   0.67242   0.46592
   0.49132   0.36293   0.19763
   0.82109   0.79176   0.69896

Maximum row and column values

Parameter two: The Matrix to compare with
Parameter three: By Rows or by column

>> a = [1 2; 3 4]
A = 1 2 3 4

>> Max (A)% maximum per column
ans =

   3   4

& Gt;> Max (A, [], 1)%
ans =

   3   4

>> Max (A, [], 2)%
ans =

   2
   4 per row max

Randperm

Generate a sequence of random sequences

>> a = [2, 3, 4, 5, 6]
A =

   2 3 4 5 6
>> rand_indices = randperm (Length (a))
rand_indices =

   1   2   4   5   3
>> A (:, Rand_indices (1:3))
ans =

   5   6   2

Custom Function Creation Step

Create the file that holds the function (the filename is the same as the function name,. m ends)

Square.m

Create a function

% A return value
function return value = function name (argument list)
    function body
end

% multiple return value function
[return value 1, return value 2] = function name (argument list)
    function body
end

Function y = Square (x)
  y = x^2;
End

function [Y1, y2] = squareandcube (x)
  y1 = x^2;
  y2 = x^3;
End

Call

Enter the directory where the function file resides

Add the directory that holds the function file to, search the path

>> CD downloads/% Enter the directory where function files are stored
>> Square (2)
ans =  4

>> addpath (' ~/downloads ')% Add to search Path
>> CD.
>> Square (2)
ans =  4

Data path

As with Linux commands

>> pwd% Current path
ans =/users/xxx

>> cd ~/developer

>> pwd
ans =/users/xxx/developer

>> ls% list directory files and folders

>> CDs.% Back to superior directory

Load and save

>> load featuresX.dat% load data, variable named Featuresx
>> data = Load (' ex1data1.txt ');% variable named data

>> save F Eaturesx.mat Featuresx; % save data in Featuresx to Featuresx file
>> save Hello.txt v-ascii% The data in variable v is encoded in ASCII mode to Hello.txt

Other commands

Simplify the command line: PS1 (' >> ');

Close the chart: closed or closing all

Command line Clear screen: CLC annotation

% Print Auto Print for comments

A = 3 will print data
a = 3;% will not print data, semicolons can prevent output

Formatting

Disp (PI)% output: 3.1416
disp (sprintf (' pi is%.2f ', pi))% C language style

Default format

Format long% modify default print format

Help

Help size% Look at the assistance document for the size function Help for

Figure Plot Properties

LineWidth: line width

Markerfacecolor: Mark Color

Markersize: Mark Size X,y axis

Ylabel (' x ');
Xlabel (' Y '); Histogram

>> W =-6 + sqrt *randn (1, 10000);
>> hist (w)
>> hist (w, 30)% 30 Group

from:https://segmentfault.com/a/1190000004204177