In an array xy=[x y], reduce array length by assigning average values of y based on a predefined range of x

I have the x values in the range x=[x1 ... xn] and y values related to x through the function f as in y=f(x). Now I want to break down down the y array to a smaller array Y in that I first find all values related to x in the range x1>x>x0 and then calculate the mean of y values whose corresponding x's are in this range. Then I move on to the next range which is x2>x>x1 and calculate the mean of the corresponding y values and so on. At the end, this will look like converting a xy larger dataset to a smaller one, as shown in the picture. Since this is usually a really large dataset, I'd rather do this without a loop.

Answer 1

[Steven Lord]

Use findgroups or discretize to bin your X data into groups then use splitapply or groupsummary to calculate the @mean for each of those groups.

[Dyuman Joshi]

This is neat. Though I found it difficult to implement the other pair - findgroups with groupsummary.

x = [(1:20)' randi(50,20,1)];
disp(x)

     1    46
     2     7
     3    40
     4    41
     5    34
     6     8
     7    38
     8    34
     9    46
    10    21
    11     8
    12     3
    13    47
    14    46
    15     4
    16    31
    17    11
    18    42
    19    21
    20    21

%Defining range of values
idx = [1 4 8 12 16 20];
out = discretize(x(:,1),idx);
splitapply(@mean, x(:,2), out)

ans = 5×1

31.0000 30.2500 27.2500 25.0000 25.2000