Finding small vector in big vector
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Lennart
le 20 Oct 2015
Modifié(e) : Bruno Luong
le 12 Mai 2024
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!
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Image Analyst
le 20 Oct 2015
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 commentaires
Image Analyst
le 21 Oct 2015
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.
Plus de réponses (2)
James Tursa
le 20 Oct 2015
Modifié(e) : James Tursa
le 20 Oct 2015
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 commentaires
Bruno Luong
le 12 Sep 2022
Modifié(e) : Bruno Luong
le 12 Mai 2024
@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))
Matlab Pro
le 12 Mai 2024
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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