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Mean of classified data

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Juanjo Gomez
Juanjo Gomez am 2 Mai 2017
Beantwortet: Mann Baidi am 7 Dez. 2023
I have a matrix X where each row represents an observation. For example:
X =
1 3
2 5
5 7
and a vector column classes that represents, for each observation in X, which class it belongs to, for example
That means observation (1,3) and (5,7) are classified as 1 and observation (2,5) is classified as 2.
I'm looking for a efficiently method to calculate the mean of each class, so in this example, I get (3,5) mean for class 1 and (2,5) mean for class 2.

Antworten (1)

Mann Baidi
Mann Baidi am 7 Dez. 2023
Hi Juanjo,
I understand you would like to perform “mean” operations on a classified 2D array.
For this you can use the “accumarray” function in MATLAB to perform arithmetic operations on classified arrays.
You can resolve your query using “accumarray” as follows:
X=[1 3;2 5; 5 7;10 15;64 67];
classes=[1 3 1 2 2]';
res=[accumarray(classes,X(:,1),[],@mean) accumarray(classes,X(:,2),[],@mean)]
res = 3×2
3 5 37 41 2 5
You can refer to the “accumarray” documentation using the following link.
Hope this will help!

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