Matlab loop inside loop

Question

I have an Nx2 matrix say D(k1,k2).I have to compare k1 and k2 from each row and switch accordingly. There is another vector d(i) which has M values. if k1 and k2 is any one value of d(i) I have to switch. if D(k1,1)==d(i)&&D(k1,2)==d(i).... Is there any method to compare all the d(i) elements in the if loop without using a for loop for i?

So if I understand correctly: you want the two elements of a row in the D matrix to switch places, when they both appear in the vector d? — Gunther Struyf
– Gunther Struyf, Commented Mar 1, 2012 at 10:29

Gunther Struyf · Accepted Answer · 2012-03-01 10:38:56Z

1

You can use the ismember function for checking if the vector d contains certain values:

D_in_d = ismember(D,d);

and then you still have to loop to perform the flipping operation on specific rows:

for i=1:size(D,1)
    if all(D_in_d(i,:))
        D(i,:)=fliplr(D(i,:));
    end
end

answered Mar 1, 2012 at 10:38

Gunther Struyf

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Comments

Geoff_Reck · Accepted Answer · 2013-02-13 17:14:17Z

0

This is relatively easy to accomplish with matlab's vectorizion without any loops at all.

% A swap logical vector ( 1 if you need to swap that row, 0 otherwise)

swap_logical = ( ismember(D(:,1),d) | ismember(D(:,2),d) );

% Vectorized swapping based on the swap boolian.

Dnew = swap_logical.*D(:,2:-1:1) + ~swap_logical.*D;

edited Feb 13, 2013 at 17:14

answered Feb 12, 2013 at 14:18

Geoff_Reck

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2 Comments

Dennis Jaheruddin Over a year ago

As ismember already provides logical output I would recommend a simple or statement: swap_logical = ismember(D(:,1),d) | ismember(D(:,2),d)

Geoff_Reck Over a year ago

I agree that is more straight forward.

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