Put a small matrix in a bigger one.

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Ayob
Ayob 2013년 6월 2일
댓글: Preet Lal 2022년 5월 20일
I want to put a small matrix (p*q) called B into a bigger matrix (m*n) called A. How can I do it. Matrix B should be put on the left-right corner of matrix A.
for better understanding take a look on this image:

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chibole
chibole 2016년 10월 19일
function A = MatrixReplace(A,B)
[p,q] = size(B);
A(end-p+1:end, end-q+1:end) = B;
end
  댓글 수: 3
Image Analyst
Image Analyst 2017년 3월 29일
Be careful with this code. For one thing, it puts the pasted matrix in the lower right corner, not at some arbitrary row and column (row "i" and column "j") like the poster asked for. It also has no error checking, has no comments, and doesn't use descriptive variable names. Personally, I would not use this code in my company. For more flexible and robust way, see my answer.
chibole
chibole 2017년 7월 22일
"For one thing, it puts the pasted matrix in the lower right corner" That is what is asked in the question.

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추가 답변 (2개)

Image Analyst
Image Analyst 2013년 6월 2일
편집: Image Analyst 2013년 6월 2일
Try this fairly robust, more general code where you can specify the upper left corner and it will check to make sure the small array does not go outside the big array.:
% Create sample data:
big = ones(10)
small = 9 * ones(3)
% Get sizes
[rowsBig, columnsBig] = size(big);
[rowsSmall, columnsSmall] = size(small);
% Specify upper left row, column of where
% we'd like to paste the small matrix.
row1 = 5;
column1 = 3;
% Determine lower right location.
row2 = row1 + rowsSmall - 1
column2 = column1 + columnsSmall - 1
% See if it will fit.
if row2 <= rowsBig
% It will fit, so paste it.
big(row1:row2, column1:column2) = small
else
% It won't fit
warningMessage = sprintf('That will not fit.\nThe lower right coordinate would be at row %d, column %d.',...
row2, column2);
uiwait(warndlg(warningMessage));
end
  댓글 수: 3
Image Analyst
Image Analyst 2022년 5월 20일
If you know the size of the matrices to be pasted onto the underlying matrix, and the locations, then you can figure out the overlap region. Then just use normal indexing to get the mean. For example if you're pasting a 2x3 into the upper left corner of a 5x5 matrix, and a 2x3 onto the upper right corner, then the last column of the first matrix you paste will overlap the left column of the second 2x3 matrix, and they are both in column 3 of the 5x5 matrix.
Preet Lal
Preet Lal 2022년 5월 20일
I am not clear,
If possible could you please share a short demo code.

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Andrei Bobrov
Andrei Bobrov 2013년 6월 2일
편집: Andrei Bobrov 2013년 6월 2일
Use function padarray from Image Processing Toolbox
A(padarray(true(size(B)),size(A)-size(B),'pre')) = B;
or
A(blkdiag(false(size(A)-size(B)),true(size(B)))) = B;

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