How to test montonousness of X Y data

I have sets of XY data with anywhere from 1 to 10 elements in it. I need to check whether x vs y is montonously increasing or not. Even if one element is out of montony then I consider the data failed to test. What is the quickest way to check this. I need to perform this on 100s of sets of XY data with verying sizes. Thanks in advance.

Answer 1

[Rik]

I would sort x, use the second output of sort to change the order of the y elements. That reduces the problem to the question whether there are any values smaller than the previous one. So using any(diff(data)<0) will give you the answer.