How to check monotonity of a vector?

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Mr M.
Mr M. 2017-12-15
评论： Andreas 2022-3-16
How to check easily that components of a vector form a monotone (increasing) sequence or not?
  1 个评论
Adam
Adam 2017-12-15
You can use
validateattributes( yourVector, { 'numeric' }, { 'vector', 'increasing' } )
if you just want to validate that it is monotonic and carry on with the code if it is while throwing an error otherwise.

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采纳的回答

KL
KL 2017-12-15
编辑：KL 2017-12-15
use diff
https://www.mathworks.com/help/matlab/ref/diff.html
along with all maybe
a = 1:10;
isIncreasing = all(diff(a)) %or all(diff(a)>=0) if you want to allow 0 difference
  1 个评论
Andreas
Andreas 2022-3-16
Ran in:
Take care, that all is also true for negative values.
Therefore, this example has a false positive on b
a = [1:10];
b = [1 2 3 2 1 5];
isIncreasingA = all(diff(a))
isIncreasingA = logical
1
isIncreasingB = all(diff(b))
isIncreasingB = logical
1
To fix that, restrict to positive values of diff
isIncreasingA = all(diff(a)>0)
isIncreasingA = logical
1
isIncreasingb = all(diff(b)>0)
isIncreasingb = logical
0

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Walter Roberson
Walter Roberson 2017-12-15
https://www.mathworks.com/help/matlab/ref/issorted.html
issorted() with 'ascend' (repeats permitted) or 'strictascend' (repeats not permitted)

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