I have some binary matrix. I want to remove all first ones from each column, but keep one if this value is alone in column. I have some code, which produces correct result, but it looks ugly- I should iterate through all columns.
Could You give me a piece of advice how to improve my code?
Non-vectorised code:
% Dummy matrix for SE
M = 10^3;
N = 10^2;
ExampleMatrix = (rand(M,N)>0.9);
ExampleMatrix1=ExampleMatrix;
% Iterate columns
for iColumn = 1:size(ExampleMatrix,2)
idx = find(ExampleMatrix(:,iColumn)); % all nonzeroes elements
if numel(idx) > 1
% remove all ones except first
ExampleMatrix(idx(1),iColumn) = 0;
end
end
I think this does what you want:
ind_col = find(sum(ExampleMatrix, 1)>1); % index of relevant columns
[~, ind_row] = max(ExampleMatrix(:,ind_col), [], 1); % index of first max of each column
ExampleMatrix(ind_row + (ind_col-1)*size(ExampleMatrix,1)) = 0; % linear indexing
The code uses:
max gives the index of the first maximum value. In this case max is applied along the first dimension, to find the first maximum of each column;