Finding a significant difference between two datasets

Hi,

I would like to find spikes in a dataset that are significantly different from a second dataset.

The picture attached shows two datasets and I would like to find the spike at 255 on the x-axis.

It would be helpful if I find these significant spikes automatically with a few commands.

I think it could be possible that I have to apply a tolerance or something that says only find data that has a greater difference than such and such (depending on the datasets that I compare).

So far I only could find the overall maximum y-value and its location but that's not what I want to find.

The output should be something like:

y = [max difference between two data sets]

x = [value at which significant difference occurs]

Answer 1

[John Chilleri]

Hello,

Given data vectors a and b of equal length, you can use the following (assuming your x values are the default 1,2,...):

x = 1:length(a);
y = abs(b-a);
[y, ind] = sort(y,'descend');
x = x(ind);

Now the vector y contains the differences sorted from largest to smallest, and the x vector contains the corresponding x values.

Hope this helps!

[Harry]

That was really helpful!

Thank you!

Answer 2

[Steven Lord]

If you're using release R2017a take a look at the isoutlier function.

[Harry]

Thank you!