how to exchange matrix rows depending on distance

hi guys, i have the following matrix A with distance D1 and matrix B with distance D2.

i want a code to exchange A rows with B rows which have higher distance, as moving row 2 in B to matrix A row 2 and remove the old row 2 in A. the output should be:

how to do this guys?

Answer 1

[Guillaume]

Hum, I'm sure I've seen a very similar question (same illustration) in the past. Is this homework?

find the index of the rows you want to exchange:

idx = find(D2 > D1);

And use that to copy the rows of B in A:

A(idx, :) = B(idx, :);

Or, using logical indexing:

A(D2>D1, :) = B(D2>D1);

[janny]

It didn't give the same answer, even the matrix came with shorter rows,i have the code as:

S = pdist(A,'minkowski',1);

S_matrix = squareform(S);

D1 = [0; diag(S_matrix,1)]

C = pdist(B,'minkowski',1);

C_matrix = squareform(C);

D2 = [0; diag(C_matrix,1)]

idx = find(D2 > D1);

A(idx, :) = B(idx, :);

fileID = fopen('outputq1.txt','w')

fprintf(fileID,'%d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d %d\r\n',A') fclose(fileID);

the output is not right. check it please. something went wrong.

[Guillaume]

I can't test your code, I don't have the stats toolbox (no pdist) and you haven't given A and B.

In any case,

   A = [1 2 3 4]'
   B = [11 12 13 14]'
   D1 = [0 14 15 16]' %as in your example
   D2 = [0 16 19 14]' %as in your example
   A(D2>D1) = B(D2>D1)

returns

   A = 
      1
      12
      13
      4

which is what you asked.

Whatever problem you're having, it's not to do with my bit of code.

[janny]

thank you very much... its working fine now,,,,

Answer 2

[MA]

clear all
close all
clc;
A=[11 22 33 44;0 14 15 16]'
B=[66 77 88 99;0 16 19 14]'
for i=1:4
    if A(i,2)<B(i,2)
        A(i,1)=B(i,1);
    end
end
A

[Guillaume]

M.A., Your loop is equivalent to:

 idx  = A(:,2)<B(:,2);
 A(idx, :) = B(idx, :);

No need for a loop.