Find average y value of a range of numbers from a non linear data set

I have a data set of around 200000 lines. The data has 2 columns say x and y. I am giving a simplified example of the same below. X = [1, 5, 7, 12, 18, 25] Y= [20, 25, 32, 28, 27, 31]

This means for x values 1 to 4 y value is 20. For x =5 and 6 y = 25. For x=7 to 11 y =25 like that. Now I want to calcate average of subsets of x with 5 numbers. For example average of y of x values 1:5, then 6:10, 11:15 etc. For example, I expect average of 6:10 subset as [25*1(y value of x=6) + 32*4(y value of 7,8,9,10)] ÷ 5. What is the simplest way for doing this in matlab. I am a beginner in matlab programming.

Answer 1

[the cyclist]

Your example of averaging the values from 6:10 would be

mean(interp1(X,Y,6:10,"previous"))

Change where I put 6:10 to be the actual range you want.

The documentation for interp1 will explain the "previous" method of interpolation, which is crucial to how this works.

You can do multiple sets of 5 at once, like this:

mean(interp1(X,Y,[1:5; 6:10]',"previous"))

The first number is the average of the first 5 elements, and the second one is the next 5.

It's easy to generalize this even further.

[math seeker]

Thank you very much for such a simple answer

Answer 2

[MARTIN FABRET]

function m = Meanfcn(X,Y,start,last)
    firstIndex = 1;
    while start < X(firstIndex)
        firstIndex = firstIndex + 1;
    end
    l = last-start;
    s = 0;
    for i=0:1:l
        if start+i>=X(firstIndex) && start+i<X(firstIndex+1)
            s=s+Y(firstIndex);
        else
            firstIndex = firstIndex+1;
            s=s+Y(firstIndex);
        end
    end
    m = s/(l+1);
end