MATLAB: Generating vector with certain element of matrix

findvector

Say, I have a matrix M = [ 4 5; 10 4; 4 7; 20 6; 4 8 ] I wanna create a vector with 4 (4's that exist only in 1st column) I can't consider 4's from 2nd column of the matrix. Answer will be : V = [4 5 7 8]

By find function, I get [4 5 ; 4 7; 4 8] but how to store them as [4 5 7 8] ?

Another question: side = find(M(1,:) == 4) gives me [4 5 ; 4 7; 4 8]. I have [4 5] already. So, I only want [4 7; 4 8] as output So, how to exclude [4 5] , or first row. I am trying to apply ~ . But, how?

Best Answer

This works:

A = [ 4 5; 10 4; 4 7; 20 6; 4 8 ];
N = 4;
Result = [N; A(A(:,1)==N,2)]';

With those column constraints, it is possible to use ‘logical indexing’ to get the result.

Related Solutions

MATLAB: Is it possible to extract the values with a vector of indices for each row without using the for statement from the matrix

see sub2ind()

A = [1, 2, 3; 4, 5, 6; 7, 8, 9; 10, 11, 12]; % reference matrix
b = [2; 1; 1; 3]; % index for each row that I want to extract
idx = sub2ind(size(A), 1:size(A,1), b.');
A(idx)

Result

>> A(idx)
ans =
     2     4     7    12

MATLAB: Divide an array in n different arrays

V = [1 1 1 1 1 1 6 6 6 6 6 6 6 6 6 3 3 3 3 3 3 3 5 5 5 5 5 5 5 8 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 4 4 4 4 4 4 4 4 4 4 2 2 2 2 2 1 1 1 1 1 6 6 6 6 6 6 6]
A = [1 3 4
6 5 2
0 8 0
0 9 0]
[~,c,a] = find(A);
[~,i] = ismember(V,a);
g = c(i);
d = find([true; diff(g); true]);
c = mat2cell(V,1,diff(d));
c{:}

Best Answer

Related Solutions

MATLAB: Is it possible to extract the values with a vector of indices for each row without using the for statement from the matrix

MATLAB: Divide an array in n different arrays

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