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Octave: matrix notes 2.
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% a : b 可以得到一个从 a 到 b 的整数组成的行向量,其中 a、b 是整数: | |
1 : 3 | |
ans = | |
1 2 3 | |
% a : b : c 可以得到一个从 a 到 c 并且相隔 b 的行向量,其中 a、b、c 都是实数: | |
1 : 2 : 10 | |
ans = | |
1 3 5 7 9 | |
% 事实上 a : b 中,a、b 也可以是实数,这样相当于 a : 1 : b 而已: | |
1.5 : 5.5 | |
ans = | |
1.5000 2.5000 3.5000 4.5000 5.5000 | |
% a == 2 可以得到一个布尔矩阵,条件成立的元素会置为 1,其中 a 是一个矩阵: | |
a = [1 2 3]; | |
a == 2 | |
ans = | |
0 1 0 | |
% [a b]、[a; b] 可以拼接矩阵: | |
a = [1 2 3; 4 5 6; 7 8 9]; | |
b = zeros(3, 3); % 3 x 3 的零矩阵 | |
[a b] | |
ans = | |
1 2 3 0 0 0 | |
4 5 6 0 0 0 | |
7 8 9 0 0 0 | |
[a; b] | |
ans = | |
1 2 3 | |
4 5 6 | |
7 8 9 | |
0 0 0 | |
0 0 0 | |
0 0 0 | |
[[[a]]] % 不管加多少中括号都是一样的 | |
ans = | |
1 2 3 | |
4 5 6 | |
7 8 9 | |
% 假设 a 是一个 m x n 的矩阵,a(:) 能把这个好端端的矩阵变成一个 (m x n) x 1 的列向量: | |
a = [1 2 3; 4 5 6; 7 8 9]; | |
a(:) | |
ans = | |
1 | |
2 | |
3 | |
4 | |
5 | |
6 | |
7 | |
8 | |
9 |
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