CODEWITHSUNDEEP
matlabnormalization
hsi
hsi

Reputation: 97

Normalize matrix to values in [0,1] by dividing by row-wise sum

I have a matrix (population, with 8 columns and 100 rows) of positive and negative numbers.

I want to create a matrix where each row has 8 real numbers which satisfy:

I wrote the code below. I tried to normalize the number in the rows but it doesn't work because the result contains negative numbers. 

population(:,1:8) = bsxfun(@rdivide,population(:,1:8).',sum(population(:,1:8).')).';

How can I fix this?

For example, the input [1 -2 3] should give the output [0.375 0 0.625]

Upvotes: 0

Views: 1671

Answers (2)

OmG
OmG

Reputation: 18838

you can do it likes the following:

col_size = size(matrix,2);
matrix = matrix - repmat(min(matrix.').', 1, col_size); % minus minimum
normal_matrix = matrix./repmat(sum(matrix, 2), 1, col_size);

using sum(matrix, 2) to get sum of rows. Then apply repmat to repeat this columnar matrix to get a matrix with size of the original matrix. Then divide the original matrix with the repeated columnar matrix.

Upvotes: 0

Wolfie
Wolfie

Reputation: 30047

You simply need to subtract the row-wise minimum (regardless whether it's negative) and divide by the row-wise sum. You can use the dim argument of min and sum to specify the value should be taken row-wise...

% Get positive values by subtractive the row-wise minimum
pos = bsxfun(@minus, data, min(data, [], 2));
% Normalise by dividing by the row-wise sum
normalized = bsxfun(@rdivide, pos, sum(pos,2));

For example:

data = [5     6     0
        6     3     2
       -1    -2     6];
pos = bsxfun(@minus, data, min(data, [], 2))
>> pos = 
      [5    6    0
       4    1    0
       1    0    8]
normalized = bsxfun(@rdivide, pos, sum(pos,2)) 
>> normalized = 
     [0.4545    0.5455         0
      0.8000    0.2000         0
      0.1111         0    0.8889]

Note: from MATLAB 2016b, the new implicit expansion methods mean you don't need bsxfun, and can simply do

pos = data - min(data, [], 2);
normalized = pos ./ sum(pos, 2);

Upvotes: 1

Related Questions