I am trying to obtain a series of vectors made of elements from a larger vector given they exceed a threshold

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I have Z=[6 7 8 5 6 7 8 3 2 4]' vector
for i=1:10; A(i) =Z(Z>Z(i)); end
For some reason its not working

Answers (2)

Matthew Eicholtz
Matthew Eicholtz on 5 Apr 2016
Edited: Matthew Eicholtz on 5 Apr 2016
The reason your code does not currently work is because you are trying to assign a vector ( Z(Z>Z(i)) ) to a scalar element in a numeric array ( A(i) ). Since the size of your vector may vary on each iteration, I suggest using a cell array.
To do this, just change A(i) to A{i}.
  3 Comments
Matthew Eicholtz
Matthew Eicholtz on 5 Apr 2016
An alternative approach if you do not want to use a cell array is to create a logical mask as follows:
Z = [6 7 8 5 6 7 8 3 2 4]';
mask = bsxfun(@gt,Z,Z');
Then, if you want to get the elements that are greater than the 4th element, for example, use:
Z(mask(:,4))

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Roger Stafford
Roger Stafford on 5 Apr 2016
It's not clear whether you want those Z elements which exceed some fixed value or those which make up a monotone increasing sequence.
For a fixed value L:
A = Z(Z>L);
For selecting only those Z which constitute a monotone increasing sequence:
t(1) = true;
for k = 2:length(Z)
t(k) = (max(Z(1:k-1))<Z(k));
end
A = Z(t);

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