How to detect differencens between 2 vectors that are sorted?

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I have to following problem: I got a vector A = [1 20 3650 4000 NaN NaN] of fixed size (here 6). Given A I generate B in such a way that I generate a new value depending on the last non-NaN value of A (in this case 4000). The new Value is now 4000*rand. For example 4000*rand = 1111. So B becomes B = [1 20 1111 3650 4000 NaN], also of fixed Size 6 and sorted. More precisely the value 1111 is appended to the vector A and then sorted so that it becomes B.
But if I just have B and A given and the knwoledge of the generation process, how can I detect the 1111? My naive approch would be, looping from 1 to end through all the elements and since I know the vectors are sorted the first missmatch is the new element. But I wondered whether their is a nicer/faster solution for this?
Thanks in advance!
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Azzi Abdelmalek
Azzi Abdelmalek el 24 de Ag. de 2015
Please give a correct example, in your example B is 1x5 not 1x6 like you said, and explain how 4000*rand is located in your new matrix?
vthuongt
vthuongt el 24 de Ag. de 2015
Thanks for your remark. I edited the question for clarification.

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Bjorn Gustavsson
Bjorn Gustavsson el 24 de Ag. de 2015
Surely this answer is what your teacher want you to learn:
setdiff(B,A)
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vthuongt
vthuongt el 24 de Ag. de 2015
Editada: vthuongt el 24 de Ag. de 2015
Thank you very much. This function seems to be exactly what I needed. I have no teacher :) This problem arouse in another larger program I am working on. But anyways- how does this function performs in contrast to the for-loop? If for example I have much bigger sets?
Bjorn Gustavsson
Bjorn Gustavsson el 24 de Ag. de 2015
I have no idea but just became curious. Please investigate and then tell us about the results.

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