How to calculate the average of each column without taking zeros values

Assume that there is a matrix:[1,3,5,0,0,0; 2,0,3,4,0,0; 3,0,0,3,0,1;4,2,2,1,8,2; 5,3,3,0,5,0; 6,7,0,0,2,0]. Display as follows

1 3 5 0 0 0

2 0 3 4 0 0

3 0 0 3 0 1

4 2 2 1 8 2

5 3 3 0 5 0

6 7 0 0 2 0

I want to calculate the average of each column without taking zeros values. The result is displayed in the corresponding column. what should I do?

Thanks in advance!

Answer 1

[Ruchika Parag]

Hi @Amy, to calculate the average of each column in a matrix while ignoring zero values, you can use MATLAB's logical indexing and array operations. Here’s how you can achieve this:

1. Create the Matrix: Define the matrix in MATLAB.
2. Calculate Averages: Iterate over each column, exclude zeros, and compute the average.
3. Display the Result: Store the averages and display them.

Here is how you can achieve this:

A = [1, 3, 5, 0, 0, 0;
     2, 0, 3, 4, 0, 0;
     3, 0, 0, 3, 0, 1;
     4, 2, 2, 1, 8, 2;
     5, 3, 3, 0, 5, 0;
     6, 7, 0, 0, 2, 0];

averages = zeros(1, size(A, 2));

for col = 1:size(A, 2)
    columnData = A(:, col);
    nonZeroData = columnData(columnData ~= 0);
    if ~isempty(nonZeroData)
        averages(col) = mean(nonZeroData);
    else
        averages(col) = NaN;
    end
end

disp('Matrix A:');

Matrix A:

disp(A);

     1     3     5     0     0     0
     2     0     3     4     0     0
     3     0     0     3     0     1
     4     2     2     1     8     2
     5     3     3     0     5     0
     6     7     0     0     2     0

disp('Column averages (ignoring zeros):');

Column averages (ignoring zeros):

disp(averages);

    3.5000    3.7500    3.2500    2.6667    5.0000    1.5000

Now, you can correctly compute and display the average of non-zero elements for each column

Answer 2

[Sandeep Mishra]

Hi Amy,

To calculate the avergae of each column without taking the zero values, you can use the MATLAB 'sum' function to calculate the total number of non zero elements along with sum of all elements in each column.

You can refer to the following code snippet:

nonZeroElement = sum(matrix~=0)
totalSum = sum(matrix)

avg = totalSum./nonZeroElement

For more information, refer to the following MathWorks Documentation to learn about ‘sum’ function: https://www.mathworks.com/help/matlab/ref/double.sum.html

I hope this help you!

Answer 3

[Star Strider]

Try thiis —

matrix = [1,3,5,0,0,0; 2,0,3,4,0,0; 3,0,0,3,0,1;4,2,2,1,8,2; 5,3,3,0,5,0; 6,7,0,0,2,0]

matrix = 6×6

1 3 5 0 0 0 2 0 3 4 0 0 3 0 0 3 0 1 4 2 2 1 8 2 5 3 3 0 5 0 6 7 0 0 2 0

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matrix(matrix == 0) = NaN

matrix = 6×6

1 3 5 NaN NaN NaN 2 NaN 3 4 NaN NaN 3 NaN NaN 3 NaN 1 4 2 2 1 8 2 5 3 3 NaN 5 NaN 6 7 NaN NaN 2 NaN

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mean_matrix = mean(matrix, 'omitnan')

mean_matrix = 1×6

3.5000 3.7500 3.2500 2.6667 5.0000 1.5000

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mean_matrix = mean(matrix, 'omitmissing')

mean_matrix = 1×6

3.5000 3.7500 3.2500 2.6667 5.0000 1.5000

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You can use either 'omitmissing' or 'omitnan' as the ‘nanflag’

.