CODEWITHSUNDEEP
matlabmatrix
Bowecho
Bowecho

Reputation: 909

Remove specific numbers from matrix and obtain a new matrix

For example, I have the matrix: 

A = [1 3 5; 
     2 7 3; 
     9 3 8];

I want to remove the number 3 from matrix A, thus obtaining a new matrix: 

B = [1 5; 
     2 7; 
     9 8];

If I try to simply remove it with A=A(A~=3), it just gives me a column vector without number 3, but I want a matrix with the exact changed size. Anyone has any idea how to do it?

Upvotes: 0

Views: 225

Answers (2)

Dan
Dan

Reputation: 45741

Generic solution:

B = arrayfun(@(r)(A(r,A(r,:)~=3)), 1:size(A,1), 'Uni', false)'

which outputs a cell array and makes no assumptions about how many 3s there are per row.

For illustration, I will rewrite the above line as a for-loop:

for r = 1:size(A,1)
    row = A(r,:)
    B(r) = row(row~=3)
end

If all your rows contain an equal number of 3s then see Santhan's answer

Or else according to your new requirements from the comments just:

A(A==3) = NaN;

or if you want to eliminate more than just one number

A(ismember(A, [2,3])) = NaN

Upvotes: 2

Santhan Salai
Santhan Salai

Reputation: 3898

One Alternate, assuming each row containing equal number of 3's

A = [1 3 5; 2 7 3; 9 3 8];
B = A.';                   %//'
out = reshape(B(B~=3),[],size(A,1)).'

Results:

A =

 1     3     5
 2     7     3
 9     3     8


out =

 1     5
 2     7
 9     8

Note: If the number of 3's in each rows are not equal, see the Generic solution by @Dan in the other answer

Or here is other alternative using mat2cell & cellfun

Code:

%// creating cells where each cell contain one row
AC = mat2cell(A,ones(1,size(A,1)),size(A,2));

%// returning only the elements not equal to 3 in each row
out = cellfun(@(x) x(x~=3),AC,'uni',0)

Results:

A =

 1     3     5     3
 2     7     3     1
 9     3     8     5


out = 

[1x2 double]
[1x3 double]
[1x3 double]

Upvotes: 2

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