How Zero padding inside a matrix ?
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Hello, how can i zero pad inside a matrix ? For example :
if true
% code
end
A = [ 1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16]
And i want
A = [ 1 2 3 4
5 6 7 8
0 0 0 0
0 0 0 0
......
0 0 0 0
0 0 0 0
9 10 11 12
13 14 15 16]
I know padarray can zero pad but only outside not in the inside.. Thank you.
采纳的回答
Star Strider
2016-5-17
Create a second matrix of zeros, then assign the appropriate rows of your first matrix to the rows you want in the second matrix:
A = [ 1 2 3 4
5 6 7 8
9 10 11 12
13 14 15 16];
Desired_Rows = 10; % Pick A Number
B = zeros(Desired_Rows, size(A,2));
B([1:2 end-1:end],:) = A
B =
1 2 3 4
5 6 7 8
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
0 0 0 0
9 10 11 12
13 14 15 16
6 个评论
So
2016-5-17
Star Strider
2016-5-17
My pleasure.
The assignment:
B([1:2 end-1:end],:) = A
creates a vector of row indices ‘[1:2 end-1:end]’ indicating the first two rows (the ‘1:2’) and the last two rows (the ‘end-1:end’), using the colon operator to create the continuity.
For your (20xN) matrix, my slightly revised code becomes:
B = zeros(size(A,1)+40, size(A,2));
B([1:10 end-9:end],:) = A
This creates a (60xN) matrix of zeros (in your example), then fills the first 10 rows of it with the first 10 rows of ‘A’ and the last 10 rows of it with the last 10 rows of ‘A’. Note that ‘end-9’ is the tenth row from the end.
Experiment with the indexing to see how it works.
So
2016-5-17
Star Strider
2016-5-17
My pleasure.
If my Answer solved your problem, please Accept it.
Guillaume
2016-5-17
In my opinion, it'd be simpler to split the original matrix and insert a zero matrix in between: B = [A(1:10, :); zeros(40, size(A, 2); A(11:20, :)]
Star Strider
2016-5-17
I thought about that, but considered that this could be a ‘proxy problem’ and the rows could end up being inserted anywhere in the target matrix, not just at the ends. The approach I took allows for that more easily.
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