CODEWITHSUNDEEP
matlabmatrixaverage
Tinashe Mutsvangwa
Tinashe Mutsvangwa

Reputation: 127

I would like to average the first n columns based on duplicate values of the n+1th column

I have a matrix with duplicate numbers in one of the columns. I would like to average the rows with duplicate numbers. For example, I have duplicate values in a matrix A in column 3:

A =   
    1         2         1
    4         4         2
    5         4         2
    4         5         2
    5         5         3
    10        3         3

I would like to get

B =
    1         2         1
    4.3333    4.3333    2.0000
    7.5000    4.0000    3.0000

where each row is the average values of the duplicate rows of column 3.

Can anyone help?

Upvotes: 0

Views: 338

Answers (1)

Eitan T
Eitan T

Reputation: 32920

The following one-liner averages all rows with duplicate values in column N.

cell2mat(arrayfun(@(x)mean(A(A(:, N)==x,:),1), unique(A(:, N)), 'Uniform', 0))

Example

Let's follow your example and average all lines with duplicates in column 3:

A = [1 2 1; 4 4 2; 5 4 2; 4 5 2; 5 5 3; 10 3 3];
N = 3;
B = cell2mat(arrayfun(@(x)mean(A(A(:, N)==x,:),1), unique(A(:,N)), 'Uniform', 0))

The result is:

B =
    1.0000   2.0000   1.0000
    4.3333   4.3333   2.0000
    7.5000   4.0000   3.0000

Upvotes: 3

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