HOW TO COMPARE TWO ARRAYS ELEMENTS IN MATLAB

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Micky
Micky 2013-2-18
I had an array AA = [ 0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3]. Then I got two arrays one shifted left one element and the other shifted right one element and padded with NaN accordingly. Example: shifted versions of arrays aa = [0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3, NaN] and second array as bb = [NaN, 0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2].
I want to compare these arrays and put the result in another array of same size,such that during comparison if the compared elements have the same sign (-/- or +/+) then the new resulted array should get NaN for that comparison entry and if the signs of the compared elements is different(-/+ or +/-), then keep the original value of the original array from where I started i.e AA.
Something like this, after comparing sign of each element of aa and bb, I should get something like this:
result = [ NaN, NaN, NaN, NaN, 0.1, -0.1, NaN, NaN]
I got the shifted versions, I just want to get some idea about comparison described above.
  1 个评论
Cedric
Cedric 2013-2-18
编辑：Cedric 2013-2-18
Do you always have this type of data and a +/- 1 shift? If so, you don't need to compare vectors to find the location of NaNs and non-NaN elements.
Also, what is the purpose of this approach?

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采纳的回答

Azzi Abdelmalek
Azzi Abdelmalek 2013-2-18
aa = [0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3, nan]
bb = [nan, 0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2]
idx=arrayfun(@sign ,aa.*bb)
AA(find(idx==1 | isnan(idx)))=nan

更多回答（2 个）

Image Analyst
Image Analyst 2013-2-18
编辑：Image Analyst 2013-2-18
Here's one way. Not really compact but at least it's explicit and easy to follow:
AA = [0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3]
aa = [0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3, NaN]
bb = [NaN, 0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2]
signAA = sign(AA)
% Process aa
signaa = sign(aa)
nanLocations = isnan(aa)
differentSignsaa = signAA ~= signaa
differentSignsaa(nanLocations) = false
% Process bb
signbb = sign(bb)
nanLocations = isnan(bb)
differentSignsbb = signAA ~= signbb
differentSignsbb(nanLocations) = false
% Create result
result= nan(1, length(AA))
% Transfer values.
indexesToTransfer = differentSignsaa | differentSignsbb
result(indexesToTransfer) = AA(indexesToTransfer)
Produces the output result you stated.
Matthew Whitaker
Matthew Whitaker 2013-2-18
Try:
AA = [ 0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3];
aa = [0.2, 0.3, 0.2, 0.1, -0.1, -0.2, -0.3, NaN];
bb = [NaN, 0.1, 0.2, 0.3, 0.2, 0.1, -0.1, -0.2];
cc = AA;
e = sign(aa)-sign(bb);
cc(e==0|isnan(e)) = NaN

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