控制语句
V =
0
0
0
0
0
0
0
0
0
0
>> for i=1:10, % for循环
> V(i) = 2 ^ i;
> end;
>> V
V =
2
4
8
16
32
64
128
256
512
1024
>> indices = 1:10;
>> for i=indices, % for循环遍历输出
> disp(i);
> end;
1
2
3
4
5
6
7
8
9
10
>> i = 1;
>> while i <= 5, % while循环
> V(i) = 100;
> i = i + 1;
> end;
>> V
V =
100
100
100
100
100
64
128
256
512
1024
>> i = 1;
>> while true,
> V(i) = 999;
> i = i + 1;
> if i == 6,
> break; % break与continue的使用
> end;
> end;
>> V
V =
999
999
999
999
999
64
128
256
512
1024
>> V(1) = 2;
>> if V(1) == 1, % if-else语句
> disp('The value is one');
> elseif V(1) == 2,
> disp('The value is two');
> else
> disp('The value is not one or two');
> end;
The value is two
函数
我们先创建costFunctionJ.m文件，并在其添加如下代码：
function J = costFunctionJ(X, y, theta)
% X is the "design matrix" contanining our tranining examples.
% y is the class labels.
m = size(X, 1); % number of tranining examples
predictions = X*theta; % predictions of hypothesis on all m examples
sqrErrors = (predictions-y).^2; % squared sqrErrors
J = 1/(2*m) * sum(sqrErrors);
然后，我们在Octave的CLI中键入如下命令：
% 先利用cd命令前往costFunctionJ.m文件目录路径
>> X = [1 1; 1 2; 1 3]
X =
1 1
1 2
1 3
>> y = [1; 2; 3]
y =
1
2
3
>> theta = [0;1];
>> j = costFunctionJ(X, y, theta)
j = 0
注：文件名需与函数名一致。
