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

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Saeid 2023-5-23

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评论： Dyuman Joshi 2023-5-24

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.

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Answer 1

Steven Lord 2023-5-24

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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.

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Dyuman Joshi 2023-5-24

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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)
  46
   7
  40
  41
  34
   8
  38
  34
  46
  21
   8
   3
  47
  46
   4
  31
  11
  42
  21
  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
0000
2500
2500
0000
2000