MATLAB: Create a 25 × 25 matrix with the command A = ones(25); Now replace the 5 × 5 submatrix between rows 11:15 and columns 11:15 with zeros.

submatrixsubstitute rows and columns

I tried the linalgsubstitute command but really didnt use it right! Help!! The implied the better

Best Answer

A=ones(25);
A(11:15,11:15)=0

Related Solutions

MATLAB: Eliminate several columns and rows of a matrix using vectors.

Try

>> m = magic( 5 )
m =
    17    24     1     8    15
    23     5     7    14    16
     4     6    13    20    22
    10    12    19    21     3
    11    18    25     2     9
% eliminate column 1,2 and 3    
>> m(:,1:3)=[]
m =
     8    15
    14    16
    20    22
    21     3
     2     9
>> m([4,5],:)=[]
% eliminate row 4 and 5
m =
     8    15
    14    16
    20    22
>> 
>> m = magic(5);
>> cols_to_eliminate = [1,3,5];
>> m(:,cols_to_eliminate) = []
m =
    24     8
     5    14
     6    20
    12    21
    18     2
>> 
>> m = magic(5);
>> cols_to_eliminate = [1,3,5];
>> rows_to_eliminate = [2,4];
>> m(rows_to_eliminate,cols_to_eliminate) = []
A null assignment can have only one non-colon index.

That doesn't work, but

>> rows_to_keep = [2,4];
>> cols_to_keep = [1,3,5];
>> m = magic(5);
>> m = m(rows_to_keep,cols_to_keep)
m =
    23     7    16
    10    19     3
>>

MATLAB: Change column and row

Hello, You can swap columns and rows quite easily in matlab. For example:

given matrix :

matrix=[1 2 3 4 5;6 7 8 9 10; 11 12 13 14 15; 16 17 18 19 20];

i can swap column 1 and 2 by performing this operation:

matrix(:,[1,2])=matrix(:,[2,1]);

for row 1 and 2, a similar operation is done:

matrix([1,2],:)=matrix([2,1],:);

Please be aware of the sequence in which you perform this operation, since column 10 and row 10 have 1 variable in common, if you swap columns and rows sequentialy, you will mix up that one variable.

Another (manual) approach to retain information is to make a copy of the row and column you want to swap in another variable such as:

copy_matrix=matrix(:,:);
matrix(2,:)=copy_matrix(1,:);
matrix(1,:)=copy_matrix(2,:);

Hope this helps,

Dennie

Best Answer

Related Solutions

MATLAB: Eliminate several columns and rows of a matrix using vectors.

MATLAB: Change column and row

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