MATLAB: Please help me to get with the scenerio mentioned

matrix manipulation

If A is a matrix of (n,m) how to group n(rows) in a random manner such that the values present in (n) in each row  should be in all the rows present in that corresponding group.
say for example
if A=(5,3)
and it has the value of [1 0 0;0 2 0;3 0 0;0 0 4;0 5 0]
after grouping in a random manner it should be [1 5 4;3 2 0;3 2 0;1 5 4;1 5 4]
(in this example row1,row4 and row5 are in one group where as row2 and row3 are in another group).
The same scenario should be applied to (n,m) indicates n number of rows and m number of columns.

Best Answer

[r,c]=find(A(1:size(A,1),:)~=0);
for i=1:numel(c)
    if sum(ismember([1 4 5],r(i)))>0
        A([1 4 5],c(i))=A(r(i),c(i));
    elseif sum(ismember([2 3],r(i)))>0
        A([2 3],c(i))=A(r(i),c(i));
    end
end

Related Solutions

MATLAB: How to generate combinatorial vectors avoiding some determinated subvectors

As far as improving the efficiency of your code, I have some questions about what you are doing.

First, I do not see how your loop is generating what you say it is. When I make it display 'a' just before the last END, the first vector is:

1    2    3    4    5    6    7    8   10

and not:

1    2    3    4    5    6    7    8   9

Second, I assume that it is right before the last END in your loop that you are using a for whatever other purpose you have, and this is where you do your check. Is that correct?

Third, I don't understand your check. In one place you say that you want to check if 'a' has any "combinatorial vectors" but later it looks like you are looking for an exact match. For example, say

a = [2 19 4 47 3]

and we want to check if 'a' contains any combinatorial of the vector

s = [4 19 47];

meaning that if a has any of these subvectors:

[4 19 47; 4 47 19; 19 4 47; 19 47 4; 47 4 19; 47 19 4]

then we will get a positive return. Your statement does not do this

TF = ismember(s,nchoosek(a,3),'rows');  % TF==0

But then later you seem to be saying that you only want to see if 'a' contains the exact vector 's', not a permutation. If this is the case, why make it so hard (and slow) using ISMEMBER and NCHOOSEK? It is much faster to do:

a = [2 4 19 47 3];  % New vector which contains vect 's'
TF = ismember(s,nchoosek(a,3),'rows');  % TF==1
TF2 = any(strfind(a,s));  %TF2==1

Once things are a little clearer, we might be able to help you speed this up even more.

MATLAB: Combination calculations and matrix manipulation

Here is how to get all of them using NPERMUTEK

A = [1 2 3 4; 
     5 6 7 8; 
     9 10 11 12];
[m,n] = size(A);
I = npermutek(1:n,m);
J = cumsum(ones(size(I)),2);
R = A(J+(I-1)*m)  % Look at each row.

If you find that NPERMUTEK gives you too many samplings, you could try one of the lesser combinatorial samplings found in this file: COMBINATOR

Best Answer

Related Solutions

MATLAB: How to generate combinatorial vectors avoiding some determinated subvectors

MATLAB: Combination calculations and matrix manipulation

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