Finding small vector in big vector
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Hey everybody,
I am desperately looking for a function that can find a small vector inside a big vector. Ismember and interesect just wouldn't do it right :(
Let's say I have the two vectors x = [ 7 6 9 7 4 3 7 9 0 7 4 3 2 6 7 0 7 5 ]; y = [ 4 3 2 6 ]
As a result I would like to have ans = [ 11 12 13 14 ]
so only the coordinates of where the values are in the correct sequence. Is there anything that can do that?
Thanks in advance!
采纳的回答
Image Analyst
2015-10-20
Try this:
x = [ 7 6 9 7 4 3 7 9 0 7 4 3 2 6 7 0 7 5 ];
y = [ 4 3 2 6 ];
% As a result I would like to have ans = [ 11 12 13 14 ]
out = strfind(x, y) + [0:length(y)-1]
2 个评论
Lennart
2015-10-21
编辑：Image Analyst
2015-10-21
Image Analyst
2015-10-21
You're welcome. strfind(x, y) finds only 11 - the start of the sequence - while adding that other vector gives you [11,12,13,14] which is what you said you wanted.
更多回答（2 个）
James Tursa
2015-10-20
编辑：James Tursa
2015-10-20
1 个投票
I am not on a machine with MATLAB at the moment to test this, but maybe try the strfind(x,y) function to see if it works with doubles (even though the doc doesn't indicate that it does).
3 个评论
Alexander
2022-9-12
It does. The numbers are internally casted to char. For compatibility with other programs you can use strfind(char(x),char(y)).
@Alexander Paul "The numbers are internally casted to char."
I don't think so, if it was, the result of the two last commands would be indentiical
d = double('a')+0.1;
a = 'a';
strfind(d,a)
strfind(char(d),char(a))
Alexander
2022-9-12
You are right. I checked it only with uint8.
Matlab Pro
2024-5-12
0 个投票
Hi
A small improvement where the sub-vector is found more than once...
x = x(:)'; % Make sure data is a Row vector
ix = strfind(x, y);
if length(ix)>1 % Fix cases where y is found more than once
idx = [1:length(y)] + ix(1)-1; % Indexes of 1st occurance
else
idx = strfind(x, y) + [0:length(y)-1];
end
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