最近学习了Octave数学软件，这个软件类似于MATLAB，但是操作要比MATLAB简单很多，上手快，对数据分析有很大的帮助，所以这里就简单的把部分练习的代码放在这里，如果你想实现一下，可以按照代码内容来，或者自己编写
GNU Octave, version 7.1.0
Copyright (C) 1993-2022 The Octave Project Developers.
This is free software; see the source code for copying conditions.
There is ABSOLUTELY NO WARRANTY; not even for MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE. For details, type 'warranty'.
Octave was configured for "x86_64-w64-mingw32".
Additional information about Octave is available at https://www.octave.org.
Please contribute if you find this software useful.
For more information, visit https://www.octave.org/get-involved.html
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For information about changes from previous versions, type 'news'.
>> 1+1
ans = 2
>> 2_4
ans = 24
>> 2-4
ans = -2
>> 2*4
ans = 8
>> 2^3
ans = 8
>> 1 == 2 % false
ans = 0
>> 1 ~= 2
ans = 1
>> 1 && 0 % and
ans = 0
>> 1 || 0 % or
ans = 1
>> xor(1,0)
ans = 1
>> a = 3;
>> disp(a)
3
>> disp(sprintf('2 decimals: %0.2f',a))
2 decimals: 3.00
>> format long
>> a
a = 3
>> b=pi;
>> b
b = 3.141592653589793
>> format short
>> b
b = 3.1416
>> A = [1 2;3 4;5 6]
A =
1 2
3 4
5 6
>> A=[1 2;
3 4;
5 6]
A =
1 2
3 4
5 6
>> v = 1:0.1:2
v =
Columns 1 through 10:
1.0000 1.1000 1.2000 1.3000 1.4000 1.5000 1.6000 1.7000 1.8000 1.9000
Column 11:
2.0000
>> v = 1:6
v =
1 2 3 4 5 6
>> ones(2,3)
ans =
1 1 1
1 1 1
>> 2*ones(3,3)
ans =
2 2 2
2 2 2
2 2 2
>> zeros(1,3)
ans =
0 0 0
>> rand(1,5)
ans =
0.388980 0.041283 0.117873 0.078976 0.599495
>> randn(2,3) %gaosi
ans =
0.814927 0.041009 -0.066768
-0.392299 -0.322274 0.081502
>> w = -6 + sqrt(10)*(randn(1,10000));
>> hist(w)
>> hist(w,100)
>> eye(10) %E function
ans =
Diagonal Matrix
1 0 0 0 0 0 0 0 0 0
0 1 0 0 0 0 0 0 0 0
0 0 1 0 0 0 0 0 0 0
0 0 0 1 0 0 0 0 0 0
0 0 0 0 1 0 0 0 0 0
0 0 0 0 0 1 0 0 0 0
0 0 0 0 0 0 1 0 0 0
0 0 0 0 0 0 0 1 0 0
0 0 0 0 0 0 0 0 1 0
0 0 0 0 0 0 0 0 0 1
>> size(A)
ans =
3 2
>> size(A, 1)
ans = 3
>> length(A)
ans = 3
>> pwd
ans = C:\Users\Administrator
>> ls
AppData
'Application Data'
Contacts
Cookies
Desktop
Documents
Downloads
Favorites
IntelGraphicsProfiles
Links
'Local Settings'
Music
'My Documents'
NTUSER.DAT
NTUSER.DAT{95de2aa9-7b20-11e9-87bd-fbd6aa594282}.TM.blf
NTUSER.DAT{95de2aa9-7b20-11e9-87bd-fbd6aa594282}.TMContainer00000000000000000001.regtrans-ms
NTUSER.DAT{95de2aa9-7b20-11e9-87bd-fbd6aa594282}.TMContainer00000000000000000002.regtrans-ms
NetHood
Pictures
PrintHood
PycharmProjects
Recent
'Saved Games'
Searches
SendTo
Templates
Videos
ntuser.dat.LOG1
ntuser.dat.LOG2
ntuser.ini
''$'\343\200\214\345\274\200\345\247\213\343\200\215\350\217\234\345\215\225'
>> cd C:/Users/Administrator/Desktop
>> load data1.txt
error: load: unable to find file data1.txt
>> load data1.dat
>> load('data1.dat')
>> who
Variables visible from the current scope:
A a ans b data1 v w
>> whos
Variables visible from the current scope:
variables in scope: top scope
Attr Name Size Bytes Class
==== ==== ==== ===== =====
A 3x2 48 double
a 1x1 8 double
ans 1x22 22 char
b 1x1 8 double
data1 97x2 1552 double
v 1x6 24 double
w 1x10000 80000 double
Total is 10230 elements using 81662 bytes
>> size(data1)
ans =
97 2
>> clear w
>> who
Variables visible from the current scope:
A a ans b data1 v
>> v = data1(1:10)
v =
6.1101 5.5277 8.5186 7.0032 5.8598 8.3829 7.4764 8.5781 6.4862 5.0546
>> save hello.mat data1.dat
warning: save: no such variable 'data1.dat'
>> save a.txt v -ascii
>> A(3,2)
ans = 6
>> A(2,:)
ans =
3 4
>> A([1 3],:)
ans =
1 2
5 6
>> A
A =
1 2
3 4
5 6
>> A(:,2)=[10,11,12]
A =
1 10
3 11
5 12
>> A = [A,[100,101,102]]
error: horizontal dimensions mismatch (3x2 vs 1x3)
>> A = [A,[100;101;102]]
A =
1 10 100
3 11 101
5 12 102
>> A(:)
ans =
1
3
5
10
11
12
100
101
102
>>
>> A = [1 2; 3 4]
A =
1 2
3 4
>> B = [5 6;7 8]
B =
5 6
7 8
>> C = [A B]
C =
1 2 5 6
3 4 7 8
>> C = [A; B]
C =
1 2
3 4
5 6
7 8
>> size(C)
ans =
4 2
>> size(C,2)
ans = 2
>> size(C,1)
ans = 4
>> A * B
ans =
19 22
43 50
>> A .* B
ans =
5 12
21 32
>> A .^ 2
ans =
1 4
9 16
>> 1 ./ A
ans =
1.0000 0.5000
0.3333 0.2500
>> log(A)
ans =
0 0.6931
1.0986 1.3863
>> exp(A) % ex
ans =
2.7183 7.3891
20.0855 54.5982
>> abs(A) % 求绝对值
ans =
1 2
3 4
>> -A
ans =
-1 -2
-3 -4
>> A + ones(length(B),1)
ans =
2 3
4 5
>> A
A =
1 2
3 4
>> A + 1
ans =
2 3
4 5
>> A' % zhuanzhi
ans =
1 3
2 4
>> max(A)
ans =
3 4
>> [val, ind]=max(A)
val =
3 4
ind =
2 2
>> find(A<3)
ans =
1
3
>> A =magic(6)
A =
35 1 6 26 19 24
3 32 7 21 23 25
31 9 2 22 27 20
8 28 33 17 10 15
30 5 34 12 14 16
4 36 29 13 18 11
>> [r , c] = find(A <= 3)
r =
2
1
3
c =
1
2
3
>> A
A =
35 1 6 26 19 24
3 32 7 21 23 25
31 9 2 22 27 20
8 28 33 17 10 15
30 5 34 12 14 16
4 36 29 13 18 11
>> sum(A)
ans =
111 111 111 111 111 111
>> prod(A) % product
ans =
3.1248e+06 1.4515e+06 2.7332e+06 3.1856e+07 2.9733e+07 3.1680e+07
>> floor(A) % 向下取整
ans =
35 1 6 26 19 24
3 32 7 21 23 25
31 9 2 22 27 20
8 28 33 17 10 15
30 5 34 12 14 16
4 36 29 13 18 11
>> ceil(A) % 向上取整
ans =
35 1 6 26 19 24
3 32 7 21 23 25
31 9 2 22 27 20
8 28 33 17 10 15
30 5 34 12 14 16
4 36 29 13 18 11
>> max(rand(3),rand(3))
ans =
0.8349 0.4311 0.8388
0.8539 0.5075 0.7513
0.9351 0.6399 0.6021
>> max(A,[],1)
ans =
35 36 34 26 27 25
>> max(A,[],2)
ans =
35
32
31
33
34
36
>> max(max(A))
ans = 36
>> max(A(:))
ans = 36
>>
>> sum(A,1)
ans =
111 111 111 111 111 111
>> sum(A,2)
ans =
111
111
111
111
111
111
>> sum(sum(A.*eye(6)))
ans = 111
>> sum(sum(A.*flipud(eye(6))))
ans = 111
>> flipud(eye(6))
ans =
Permutation Matrix
0 0 0 0 0 1
0 0 0 0 1 0
0 0 0 1 0 0
0 0 1 0 0 0
0 1 0 0 0 0
1 0 0 0 0 0
>> pinv(A) % 伪逆矩阵
ans =
1.1532e-02 -3.8622e-02 2.5421e-02 5.3595e-03 -1.3931e-02 1.9248e-02
2.2731e-03 -2.0103e-02 1.6162e-02 1.4619e-02 -3.2449e-02 2.8508e-02
-8.1436e-03 3.0447e-03 -1.5088e-02 4.2021e-03 2.7736e-02 -2.7423e-03
5.3971e-02 -4.1708e-02 -1.5849e-03 6.0143e-02 -6.6400e-02 4.5879e-03
-4.0937e-02 2.3106e-02 2.8508e-02 -5.3282e-02 3.5452e-02 1.6162e-02
-9.6868e-03 8.3292e-02 -4.4409e-02 -2.2032e-02 5.8600e-02 -5.6755e-02
>> inv(A)
warning: matrix singular to machine precision, rcond = 4.80096e-18
ans =
3.7530e+14 4.7714e-02 -3.7530e+14 -3.7530e+14 9.3750e-02 3.7530e+14
3.7530e+14 6.6233e-02 -3.7530e+14 -3.7530e+14 6.2500e-02 3.7530e+14
-1.8765e+14 -4.0123e-02 1.8765e+14 1.8765e+14 -1.5625e-02 -1.8765e+14
-3.7530e+14 -1.2804e-01 3.7530e+14 3.7530e+14 -1.5625e-01 -3.7530e+14
-3.7530e+14 -6.3230e-02 3.7530e+14 3.7530e+14 -6.2500e-02 -3.7530e+14
1.8765e+14 1.2646e-01 -1.8765e+14 -1.8765e+14 1.0938e-01 1.8765e+14
>> pinv(A)*A
ans =
0.777778 -0.222222 0.111111 0.222222 0.222222 -0.111111
-0.222222 0.777778 0.111111 0.222222 0.222222 -0.111111
0.111111 0.111111 0.944444 -0.111111 -0.111111 0.055556
0.222222 0.222222 -0.111111 0.777778 -0.222222 0.111111
0.222222 0.222222 -0.111111 -0.222222 0.777778 0.111111
-0.111111 -0.111111 0.055556 0.111111 0.111111 0.944444
>>
>>
>> t = [1 2 3 4 5 6 7 8 9]
t =
1 2 3 4 5 6 7 8 9
>> y1= sin(pi*4*t)
y1 =
Columns 1 through 7:
-4.8984e-16 -9.7969e-16 -1.4695e-15 -1.9594e-15 -2.4492e-15 -2.9391e-15 -3.4289e-15
Columns 8 and 9:
-3.9187e-15 -4.4086e-15
>> plot(t,yi)
error: 'yi' undefined near line 1, column 8
>> plot(t,y1)
>> hold on;
>> plot(t,y1,'r')
>> xlabel('time')
>> ylabel('value')
>> print -dpng 'myFirstPlot.png' % 图片储存
>> close
>> figure(1);plot(t,y1)
>> figure(2);plot(t,y1)
>> subplot(1,2,1)
>> plot(t,y1)
>> subplot(1,2,2)
>> plot(t,y1)
>> axis([0.5 1 -1 1])
>> iamgesc(A)
error: 'iamgesc' undefined near line 1, column 1
>> imagesc(A)
>> imagesc(A),colorbar,colormap gray;
>> close
>> pwd
ans = C:\Users\Administrator\Desktop
>> squarThisNumber(10)
error: 'squarThisNumber' undefined near line 1, column 1
>> squareThisNumber(10)
ans = 100
squareThisNumber.m函数：
注意：文件的命名应该和函数名相同，否则无法调用函数！！
function y = squareThisNumber(x)
y = x^2;
costFunctionJ.m函数：
function j = costFunctionJ(X, y, theta)
% X 是设计函数，就是训练样本数
% y 分类标签
m = size(X, 1); % 计算训练样本个数（行数）
prediction = X * theta;
sqrErrors = (prediction - y).^2;
J = 1/(2*m)*sum(sqrErrors); %主函数
