Porblem with indexing using a loop

The idea is to find indices of K smallest values from every column of matrix "lag", but when you run the code you will see that the resulted matrix "indices" gives only "0" and only one column gives result.

Could anyone help to handle this problem.

clear;
% import the data which should be a vector of (X, Y, Z, Value)
data=xlsread('raw5x5example.csv'); 
% Insert the coordinate properties of target blocks
x0= 0; y0=0;z0=0;% origin
nx = 5; ny = 5; nz = 1; % number of blocks along X, Y, and Z
dx = 1; dy= 1; dz= 1; % dimension of blocks along X, Y, and Z 

block = [x0 + kron(ones(ny*nz,1),dx*[0:nx-1]'), y0 + kron(kron(ones(nz,1),dy*[0:ny-1]'),ones(nx,1)), z0 + kron(dz*[0:nz-1]',ones(nx*ny,1))];

% initialize the array of lags
lag = ones(size(block,1),size(block,1));

% calculation of lags between all points
for i=1:size(block,1)    
    d=ones(size(data,1),1)*block(i,1:3)-data(:,1:3);
    lag(:,i)=ones(size(data,1),1).*sqrt(d(:,1).^2+d(:,2).^2+d(:,3).^2);
end

% number of points to consider in kNN
k = 6; 
% initialize the variable "smallest_N_values_lag"
smallest_N_values_lag = zeros(k,size(block,1));

for i=1:size(block,1)
    % get the k-smallest numbers from the i-th column of array lag
    smallest_N_values_lag(:,i) = mink(lag(:,i), k);
    % initialize the array of indices
    indices = zeros(k, size(block,1));
    % initialize counter
    count = 1;
    % loop over all the num-smallest numbers
    
    for j = 1:k
        % check for multi-occurrence of a component
        if j > 1
            if smallest_N_values_lag(j, i) == smallest_N_values_lag(j - 1, i)
                count = count + 1;
            else
                count = 1;
            end
        end
                      
        % find the indices of the component in the i-th column of array Lag
        idx = find(lag == smallest_N_values_lag(j, i));
    
        % place the found index in the array of indices appropriately
        indices(j, i) = idx(count);
    end

end

Answer 1

[Jan]

You overwrite the array indices in each iteration:

% Move here  <------------------------------------\
for i=1:size(block,1)                   %         |
    ...                                 %         |
    indices = zeros(k, size(block,1));  % --> ----/
    ...
    for j = 1:k
        ...
        indices(j, i) = idx(count);
    end
end

Move the creation by indices=zeros() before the "for i" loop.

[Iliqe]

thank you for your help)

Haven't noticed such an obvious mistake.