Average number of y for y=f(x) where there are several y values for the same x

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Saeid 2022-2-4

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https://ww2.mathworks.cn/matlabcentral/answers/1643415-average-number-of-y-for-y-f-x-where-there-are-several-y-values-for-the-same-x

回答： Voss 2022-2-4

采纳的回答： Voss

I have an array y where y is a function of x but for every x there are multiple values of y.

x=[x1 x1 x1 x1 x1 x2 x2 x2 x2 x3 x3 x3 x3 x3 ...]

y=[y1 y2 y3 y4 y5 y6 ... yn]

How can I separate the values of y related to each unique x and e.g. calculate their average (or maximum or minimum) to have an array of unique x and y elements at the end that would look like this:

x=[x1 x2 x3 ... xn]

y=[mean(y1:y5) mean(y6:y9) mean(y10:y14)...]

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Answer 1

Voss 2022-2-4

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在 MATLAB Online 中打开

% creating some x and y to replicate your situation, as I understand it:
x = repelem([1 2 3 4],1,5);
y = randn(size(x))+repelem(2:2:8,1,5);
disp(x); disp(y);
     1     1     1     1     1     2     2     2     2     2     3     3     3     3     3     4     4     4     4     4

    2.0493    1.9038    2.2196    0.8905    1.6911    5.0208    3.4631    5.1964    3.8335    4.7127    5.7153    5.3221    7.5308    5.2093    4.9359    9.5675    8.4060    7.6161    7.4658    8.1718
% Perform the requested task, as I understand it:
[ux,~,jj] = unique(x);
nux = numel(ux);
uy = zeros(1,nux);
for ii = 1:nux
    uy(ii) = mean(y(jj == ii));
end
disp(ux); disp(uy);
     1     2     3     4

    1.7509    4.4453    5.7427    8.2455