Return vectors from for loop as columns in matrix

Hi, I have a 296x6 matrix called normalimpact, and i want to assign random weights to each column of the matrix, do some scoring and ranking operations, and repeat this for a certain number of trials (say 10), and ouput the result from each trial (the column vector RankOfNode) as a column in a matrix. Each iteration's result of RankOfNode) should be its own column in a final matrix.

I'm just confused as how to implement the index for the number of runs into this code, since there already are a lot of for loops and indices.

normalimpact = horzcat(NormalPowerN1f, NormalICTN1f, NormalPowerN2f, NormalICTN2f, NormalPowerN3f, NormalICTN3f);

% for loop to do a bunch of runs of this code with different weights each time???? 

    % weight the matrix, giving a weight to each column
    weights = rand(1,6);
    weights = weights / sum(weights);
    normalimpactw = bsxfun(@times, normalimpact, weights);


    max_vals = max(normalimpactw); % maximum values of each colum(1 to 6 ) 
    Dplus = zeros(size(normalimpactw,1), 1); % initialize 
    for ii =1: size(normalimpactw, 1 ) 
        Dplus(ii, :) = sqrt(sum([normalimpactw(ii,:)-max_vals].^2 )); 
    end 
    Dplus; % column matrix after calculation 

    min_vals = min(normalimpactw); % minimum values of each column(1 to 6 ) 
    Dminus = zeros(size(normalimpactw,1), 1); % initialize 
    for ii =1: size(normalimpactw, 1 ) 
        Dminus(ii, :) = sqrt(sum([normalimpactw(ii,:)-min_vals].^2 )); 
    end 
    Dminus; % column matrix after calculation 
    
    % give score to each row of matrix based on values for Dplus and Dminus
    Sscore = zeros(size(Dminus,1),1);
    for n=1:296
     Sscore(n,:) = Dminus(n,:)/(Dminus(n,:)+Dplus(n,:));
    end
    
    % produces the rank for each node, ie node 1 has rank 50, node 2 has rank 23
    [~,rank] = ismember(Sscore,sort(Sscore,'descend')); 
    RankOfNode = rank;
% end of for loop????

Answer 1

[Jan]

Start with cleaning up the code.

• The lines Dplus; and Dminus; do nothing, so they are wasting time only and confuse the readers.
• Are you running a Matlab version >= R2016b? Then you can omit the bsxfun() calls and use implicit expanding.
• The loops can be omitted also:

% Replace:
    Dminus = zeros(size(normalimpactw,1), 1); % initialize 
    for ii =1: size(normalimpactw, 1 ) 
        Dminus(ii, :) = sqrt(sum([normalimpactw(ii,:)-min_vals].^2 )); 
    end 
    Dminus;
 % by
    Dminus = vecnorm(normalimpactw - min_vals, 2, 2);
 % Or with older Matlab versions:
    tmp    = bsxfun(@minus, normalimpactw, min_vals);
    Dminus = sqrt(sum(tmp .^2, 2));

• Do you really need ismember, or do you want the sorting order?

Together:

normalimpact = horzcat(NormalPowerN1f, NormalICTN1f, NormalPowerN2f, NormalICTN2f, NormalPowerN3f, NormalICTN3f);
% for loop to do a bunch of runs of this code with different weights each time???? 

% weight the matrix, giving a weight to each column
    weights = rand(1,6);
    weights = weights / sum(weights);
    normalimpactw = normalimpact .* weights;
    
    max_vals = max(normalimpactw); % maximum values of each colum(1 to 6 )
    Dplus    = vecnorm(normalimpactw - max_vals, 2, 2);
    
    min_vals = min(normalimpactw); % minimum values of each column(1 to 6 ) 
    Dminus   = vecnorm(normalimpactw - min_vals, 2, 2);
    
    Sscore   = Dminus ./ (Dminus + Dplus);
    % Is this meant?  ^^ elementwise devision?

    [~, RankOfNode] = sort(Sscore,'descend'); 

Now including this in a for loop might be easier.

    for k = 1:10
        ...
        [~, RankOfNode(k, :)] = sort(Sscore, 'descend');
        % [EDITED]         ^ orphaned "]" removed here
    end

Or maybe you want to collect the output in a cell array?

[Emma Kuttler]

Thanks for your help! I think i do need to use ismember in order to break ties. Is there a way to use my original sorting code with a loop? The rest of the cleanup works well and returns the same values.

[~,rank] = ismember(Sscore,sort(Sscore,'descend')); 
    RankOfNode = rank;

Additionally, your suggestion of

    
  for k = 1:10
        ...
        [~, RankOfNode(k, :])] = sort(Sscore, 'descend');    
    end

does not work, it returns:

Invalid expression. When calling a function or indexing a variable, use parentheses. Otherwise, check for mismatched delimiters.

When i remove a parentheses or bracket, it give me an error of:

Unable to perform assignment because the size of the left side is 1-by-1 and the size of the right side is 296-by-1.

[Jan]

@Emma: There was a typo in my code and the "]" must be removed. collecting the data inside RankOfNode works only, if this variables is pre-allocated with the matching size. So either use:

RankOfNode = zeros(296, 10);
for k = 1:10
   % the rest of the code comes here
   [~, RankOfNode(:, k)] = sort(Sscore, 'descend');    
end

Or collect the values in a cell array at first:

RankOfNodeC = cell(1, 10);
for k = 1:10
   % the rest of the code comes here
   [~, RankOfNodeC{k}] = sort(Sscore, 'descend');    
end
RankOfNode = cat(2, RankOfNodeC{:});