calculate distances between the rows of a matrix through an iterative process

Hello,

Consider a matrix 100x10, denoted as A, and the first row of A

row1=A(1,:);

I calculate the Euclidean distances between row1 and A and I found the closest row to row1, denoted as row_a.

Then I exclude the row1 from A (which becomes 99x10) and calculate the distances between row_a and the new A.

I find again the closest row to row_a, denoted as row_b, and exclude the row_a from the new A (which becomes 98x10). Then I calculate the distances between row_b and the new A and so on.

How can I do this iterative process with a loop?

Thank you very much.

Best,

Natasha

Answer 1

[Sean de Wolski]

Build an index vector of rows to keep when doing the comparison: pseudocode

row_of_interest = 10;  %initial row of interest
rows_to_keep = 1:100;  %rows that have not yet been the closest
rows_closest_storage = zeros(1,100); %storage vector for closest rows

for ii = 1:99
  row_closest = compare_rows_etc. %get the closest row
  rows_to_keep(rows_to_keep==row_of_interest) = []; %remove the original row_of interest
  rows_closest_storage(ii) = row_of_interest; %store it
  row_of_interest = row_closest; %continue
end

[Natasha Kratowska]

Thank you for your response.

I use the pseudo-code but i get the message:

Error using == Matrix dimensions must agree.

The message appears after the 3rd iteration (ii=3) from the ii=1:99.

[Natasha Kratowska]

This is my code:

row_of_interest = 10;

rows_to_keep = 1:100;

rows_closest_storage = zeros(1,100);

for ii = 1:99

 row_closest = pdist2(A(ii,:),A(row_of_interest,:));

rows_to_keep(rows_to_keep==row_of_interest) = [];

rows_closest_storage(ii) = row_of_interest;

row_of_interest = row_closest;

end