d*******2
发帖数: 340 | 1 比如4x3的矩阵，现有一向量a=[0 0 0]; 如何找到他的行号是第四行？先谢了！
0 0 20
0 5 10
4 9 4
0 0 0 |
r****x
发帖数: 3613 | 2 row = find(a==[c c c])
【在 d*******2 的大作中提到】
: 比如4x3的矩阵，现有一向量a=[0 0 0]; 如何找到他的行号是第四行？先谢了！
: 0 0 20
: 0 5 10
: 4 9 4
: 0 0 0
|
d*******2
发帖数: 340 | 3 >> a=[0 0 20; 0 5 10; 4 9 4; 0 0 0];
a =
0 0 20
0 5 10
4 9 4
0 0 0
>> row = find(a==[0 0 0])
??? Error using ==> eq
Matrix dimensions must agree.
【在 r****x 的大作中提到】
: row = find(a==[c c c])
|
r****x
发帖数: 3613 | 4 sorry, i tried the new one.
[row,col]=find(a==[0]);
for i=1:4
if a(i,1)==a(i,2) && a(i,1)==a(i,3) && a(i,1)==0
i
end
end
i =
4
【在 d*******2 的大作中提到】
: >> a=[0 0 20; 0 5 10; 4 9 4; 0 0 0];
: a =
: 0 0 20
: 0 5 10
: 4 9 4
: 0 0 0
: >> row = find(a==[0 0 0])
: ??? Error using ==> eq
: Matrix dimensions must agree.
|
r****x
发帖数: 3613 | 5 i can't find any simple pre designed matlab functions.
【在 r****x 的大作中提到】
: sorry, i tried the new one.
: [row,col]=find(a==[0]);
: for i=1:4
: if a(i,1)==a(i,2) && a(i,1)==a(i,3) && a(i,1)==0
: i
: end
: end
: i =
: 4
|
t***s
发帖数: 4666 | 6 find(ismember(A,a,'rows'))
【在 d*******2 的大作中提到】
: 比如4x3的矩阵，现有一向量a=[0 0 0]; 如何找到他的行号是第四行？先谢了！
: 0 0 20
: 0 5 10
: 4 9 4
: 0 0 0
|
d*******2
发帖数: 340 | 7 Thank you very much and admire you very much!
【在 t***s 的大作中提到】
: find(ismember(A,a,'rows'))
|
j****x
发帖数: 943 | 8 Just curious, isn't "find" pretty slow? any other alternatives? Only for
matlab or using python? |
i******t
发帖数: 370 | 9 This code is more efficient though harder to read:
e = A-repmat(a, [size(A, 1), 1]);
i = find(sum(e==0, 2)==size(A, 2));
"find" only operates on a vector so it's fast.
【在 j****x 的大作中提到】
: Just curious, isn't "find" pretty slow? any other alternatives? Only for
: matlab or using python?
|
b****r
发帖数: 5889 | 10 那这样会快点吗
find(ismember(A',a','column'))
【在 i******t 的大作中提到】
: This code is more efficient though harder to read:
: e = A-repmat(a, [size(A, 1), 1]);
: i = find(sum(e==0, 2)==size(A, 2));
: "find" only operates on a vector so it's fast.
|
|
|
t***s
发帖数: 4666 | 11 find(ismember()) operates on a vector too. hehe.
i don't know how ismember is implemented.
【在 i******t 的大作中提到】
: This code is more efficient though harder to read:
: e = A-repmat(a, [size(A, 1), 1]);
: i = find(sum(e==0, 2)==size(A, 2));
: "find" only operates on a vector so it's fast.
|
c****w
发帖数: 565 | 12 naive to argue about function speed under MATLAB, if you want speed, forget
about MATLAB |
g****y
发帖数: 199 | 13 even for Matlab, high speed is always better, and those discussions are also
helpful. don't be too picky:)
forget
【在 c****w 的大作中提到】
: naive to argue about function speed under MATLAB, if you want speed, forget
: about MATLAB
|
i******t
发帖数: 370 | 14 The speed matters.
If you have a matlab code written in 3 recursive loops with 100 iterations
each, you will need to optimize the code...
forget
【在 c****w 的大作中提到】
: naive to argue about function speed under MATLAB, if you want speed, forget
: about MATLAB
|
d*******2
发帖数: 340 | 15 I guess 99% of people who complain matlab's speed are not using matlab
properly, although you might be the rest 1%.
forget
【在 c****w 的大作中提到】
: naive to argue about function speed under MATLAB, if you want speed, forget
: about MATLAB
|
p*****o
发帖数: 40 | 16 er...
【在 d*******2 的大作中提到】
: I guess 99% of people who complain matlab's speed are not using matlab
: properly, although you might be the rest 1%.
:
: forget
|
