Octave basic syntax

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Octave Basic functions

Generating matrix functions

• eye(n)： Generate n That's ok n The unit matrix of the column
• rand(n,m)： Random generation n That's ok m The column size range is 0~1 Random number between
• randn(n,m)： Generate according to Gaussian distribution n That's ok m Random number of columns
• ones(n,m)： Generate n That's ok m The column elements are 1 Matrix
• zeros(n,m)： Generate n That's ok m The column elements are 0 Matrix

Matrix operation function

• B = A(n:m)： The matrix A Of the n Go to the first place m The value of the row is assigned to the matrix B
• A(n,m)： take n That's ok m Column elements
• A([1 3],: )： The matrix A All the elements in the first and third lines are shown
• A(2,: )： The matrix A All the elements in the second line show up
• A = [A,B]： Base B Extended to matrix A To the right of , And assign the new matrix to A
• A = [A;B]： Base B Extended to matrix A Below , And assign the new matrix to A
• A(: )： take A All the elements in the column form a new column vector according to the direction of the column
• reshape(A(i:j), n, m)：A It's a column vector ,i and j Denotes the th of the column vector i Items to j The term is taken out and reorganized into another matrix ,n and m They are the corresponding rows and columns after reorganization

Matrix operations

• a*b : matrix multiplication
• a.*b： Multiply each element
• a.^2： Square the elements
• 1./a： Yes a The reciprocal of the elements of
• log（a）： Find logarithm
• exp（a）： With e Bottom , With a Is a power
• abs（a）： Find the absolute value
• v+ones（length（v）,1）： Yes v The element of plus 1
• A’：A The transpose
• prin（A）： Inverse or pseudo inverse
• sum(a)： Sum the data in the matrix
• prod(a)： The product of
• floor(a)： Rounding up
• ceil(a)： Rounding down
• max(A,[],1)： Take the maximum value of each column
• max(A,[],2)： Take the maximum of each row
• max（max（A））： The maximum in the matrix

Make a simple picture

• plot(x,y)： With x Abscissa ,y The vertical coordinates are plotted , The third parameter is optional , Represents the image type ('r’ The color is red )
• hold on： Put multiple pictures in the same image . usage ： Draw... First plot(t,y1); And then in and out of hold on; And then input plot(t,y2), That is, two images can be displayed at the same time
• xlabel(xString)：xString Express x The name of the axis
• ylabel(yString)：yString Express y The name of the axis
• legend(string1, string2…)： Name each curve in the drawing order
• title(tString)：tString Indicates the name of the chart
• print -dpng ‘file.png’： Save the chart as png picture
• close： Turn off the currently open chart
• figure(n)： Use plot Use this function before the function , Guarantee n Different , Multiple chart windows can be opened without being covered
• subplot(1,2,1)： Divide the drawing into 1*2 The grid of , Use the first grid when drawing
• axis([x1,x2,y1,y2])： Set scale value ,[x1,x2] Is the scale range of the horizontal axis ,[y1,y2] Is the scale range of the vertical axis
• imagesc(A)： For matrix A Draw a color matrix , Different values correspond to different color depths

Common operations

• PS1(">> “)： Change the command line preamble to ”>> "
• size(A,[N])：A For a matrix , When the first parameter is omitted, the function returns an array [n,m], among n by A Row number ,m by A Columns of ; The second parameter is optional , Represents the dimension of a matrix , Back to page N Dimension of dimension . for example

A = 1
	2
    3
    4
    5
    6
    7
    8
    9
size(A) = 9 1
size(A,1) = 9
size(A,2) = 1

• disp()： Print variables or strings
• pwd： Show current path
• load： Load data file
• who： Query the variable name in the workspace
• whos： Query the details in the workspace
• clear： Clear a variable (clear x), if clear There is no variable after , All variables are cleared
• clc： Clear the screen
• save file A： take A The matrix is stored in a file file in