# Machine Learning--octave Matrix operation (2)--day3

Source: Internet
Author: User
Tags cos sin

Mathematical operations of matrices:

Assumed:a is a matrix,m is a vector

Log (a)--a logarithm of each element

Exp (a)--base e index

1./a--The mentor of every element

[A,b]=max (m)--m is a vector,a is the largest element in m , andb is a ordinal number in m (from small to large row)

M<3--such as m=[1 6 7], will be [1 0 0](should be able to understand)

Find (m>3)--such as m=[1 6 7], will get [2 3], that is , the subscript of the element greater than 3 (should be able to understand)

Magic (3)--produces a 3*3 matrix, with each row added equal to each column .

[C,d]=find (A>3)--Finds all elements greater than 3 in the a matrix , andC returns rows ,D returns the column

SUM (m)--Sum

Prod (m)--Product

Floor (m)--Rounding down

Ceil (m)--Rounding up

Max (a,[],1)--Take the maximum value of each column

Max (a,[],2)--Take the maximum value of each row

Sum (a) or sum (a,1)--Sum each column

SUM (a,2)--sum each line

SUM (SUM (A.*eye (3))-- a matrix of the diagonal elements of A and (a is a 3*3 )

Max (A (:))--Find The largest element in a matrix

Flipud (a)--Flips The matrix up and down

SUM (SUM (A.*flipud (eye (3)))-- The sum of a pair of diagonal elements (a is 3*3 The Matrix)

Drawing:

Plot (x, y)-- is the dependent variable andy is the argument

On

Plot (x1,y1, ' R ')--Put the picture above the old figure, the color is red

Xlabel (")--Give the argument a name

Ylabel (")--Give the dependent variable a name

Legend (",")--Legend

How to save a picture in MATLAB:

1, You can use the print command to save:
Print (1, '-djpeg ', ' picname.jpeg ')
Note: The first parameter represents the handle number of the graphics window, the second argument, in quotation marks, is saved in the JPEG format, and the third parameter is the file name.
2, can be saved with the SaveAs command:
SaveAs (GCF, ' picname ', ' jpg ')
Note: The first parameter is the function name Matlab obtains the graphics handle number, the second parameter, in quotation marks is the file name that you want to save, do not write the suffix here, the third parameter is the file type.

3.Figure (1);p lot (); --Numbering the graph

In 4.matlab, subplot (m,n,p) can draw an mxn Sub-chart in a figure, P can specify the position of the sub-graph, in general P is a single number,p is a vector can be combined with multiple sub-graphs as a sub-graph.

1. Clear
2. Clc
3. X=-4*pi+eps:0.01:4*pi;
4. Y1=sin (x);
5. Y2=cos (x);
6. Y3=tan (x);
7. Figure
8. Subplot (2,2,1);p lot (x,y1), title (' Sin (x) ')
9. Subplot (2,2,2);p lot (x,y2), title (' cos (x) ')
10. Subplot (2,2,[3,4]);p lot (x,y3), title (' Tan (x) ')% merges two of the second row into one
11. Figure
12. Subplot (2,2,[1 2]);p lot (x,y1), title (' Sin (x) ')% merges two of the first row into one
13. Subplot (2,2,3);p lot (x,y2), title (' cos (x) ')
14. Subplot (2,2,4);p lot (x,y3), title (' Tan (x) ')
15. Figure
16. Subplot (2,2,[1 3]);p lot (x,y1); title (' Sin (x) ')% merge two of the first column into one
17. Subplot (2,2,2);p lot (x,y2), title (' cos (x) ')
18. Subplot (2,2,4);p lot (x,y3), title (' Tan (x) ')
19. Figure
20. Subplot (2,2,1);p lot (x,y1), title (' Sin (x) ')
21. Subplot (2,2,3);p lot (x,y2), title (' cos (x) ')
22. Subplot (2,2,[2 4]);p lot (x,y3), title (' Tan (x) ')% merges two of the second column into one
23. 5.axis ([1 2 3 4]) --Set x axis is ( the ), y The axis range is set to ( 3 , 4)

5.axis ([1 2 3 4])--Set the x axis to (+) and they - axis range to (3 , 4 )

6.Imagesc (a)--Visual matrix

7.Imagesc (a), Colorbar,clolormap gray; --Black and white (amount, bad description, as below)

Machine Learning--octave Matrix operation (2)--day3

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