MATLAB: Insert rows from one matrix into another that share the same column numbers

MATLABmatrix array

I have a matrix that looks like this

M = [0 2011 1 0 0
     0 2011 1 1 0
     0 2011 1 2 0
     0 2011 1 3 0]

and one that looks like this

 N = [1 2011 1 0 399.15
      1 2011 1 1 399.93
      1 2011 1 2 399.52
      1 2011 1 3 399.59]

How do insert data from N into M if it matches the numbers in columns 2 through 4?

Best Answer

[found, idx] = ismember(N(:,2:4), M(:,2:4), 'rows');
M(idx(found), 5) = N(found,5);

However the code in this form will not work for the situtation where there are multiple matches (on either side), in which case you would need to clarify what "insert" meant. If there were multiple sources, should they be totaled, or averaged, or the maximum taken, or ?

Related Solutions

MATLAB: How to add elements to a matrix one-by-one

Hi,

I tried to fix the errors (cut and paste some lines inside the inner for loop), and added outer for loop for 10 times calculation(I assume your random variable a changes in every iteration).

Try this below. It takes a little bit long time since I ended up with conmat 2048x2048 matrix. But maybe there could be a high performanced version of it.

conmat = [0 1; 1 0] ;
for m=1:10
    S=size(conmat,1);
    r=randi(S);
    sigma=0.3;
    a=rand;
      
    for j=1:size(conmat,1)
        rowadd=zeros(1,size(conmat,1));
        rndrow=conmat(r,:);
        if sigma > a
            rowadd= rndrow;
        elseif sigma < a
            %         rowadd(j)= 0
        end
        conmat=[conmat; rowadd]; %ERROR
        coladd=transpose(conmat(3,:));
        coladd=[coladd; 0];
        conmat=[conmat coladd];
    end   
end

If you want to replicate matrices you can use repmat function also. Here the link: repmat

MATLAB: How to write a function to find a value from a table.

I would use the interp1 function.

You can easily make a function from it:

M = [ 250 1.003 0.716 1.401
      300 1.005 0.718 1.400
      350 1.008 0.721 1.398
      400 1.013 0.726 1.395];
CpCvk = @(TK) interp1(M(:,1), M(:,2:4), TK, 'linear', 'extrap');
T325 = CpCvk(325)
T325 =
       1.0065       0.7195        1.399

Best Answer

Related Solutions

MATLAB: How to add elements to a matrix one-by-one

MATLAB: How to write a function to find a value from a table.

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