MATLAB: Storing the index of an Matrix for non zeros

indexingmatlab function

i want to store the index values of non zero values in a vector (row instead of col )

Best Answer

In just two lines, no loop required:

>> X = [1,0,2;0,1,1;0,0,4]
X =
     1     0     2
     0     1     1
     0     0     4
>> [C,R] = find(X.');
>> Z = accumarray(R,C,[],@(v){v});

And checking:

>> Z{:}
ans =
     1
     3
ans =
     2
     3
ans =
     3

Related Solutions

MATLAB: How to replace the elements row by rows instead of column by column in matrix

find(A==3,1,'first')
find(A==3,1,'last')

These lines find linear indices not [row, col] subsets. Linear indices go along all the rows of the first column, then on to the second column and so on.

These two lines also disregard i and j completely, so they always give the absolute first and last linear indices in the entire matrix each iteration (5 and 18).

I dont know what exactly you're trying to achieve, but maybe you need to compare only current row:

index_1 = find(A(i,:)==3,1,'first');
index_2 = find(A(i,:)==3,1,'last');

Look here for explanation on array indexing in Matlab

if A(i,j)=3 & A(i,j)==index_1

This condition compares the value of A(i,j) to 3 and to the first index which equals 3, that makes little sence to me, but i may be missing your intent

If you explain with more detail what you are trying to do, we may be able to help you get to the right solution

MATLAB: Check if any elements of cell array are equal

Matching:

>> a{1}=[1,1,0];
>> a{2}=[9,9,9,9];
>> a{3}=[1,1,0];
>> a{4}=[];
>> N = numel(a);
>> [X,Y] = ndgrid(1:N);
>> Z = tril(true(N),-1);
>> any(arrayfun(@(x,y)isequal(a{x},a{y}),X(Z),Y(Z)))
ans = 1

vs. non-matching:

>> a{1}=[1,1,1];
>> any(arrayfun(@(x,y)isequal(a{x},a{y}),X(Z),Y(Z)))
ans = 0

Best Answer

Related Solutions

MATLAB: How to replace the elements row by rows instead of column by column in matrix

MATLAB: Check if any elements of cell array are equal

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