How to add a first row and a first column of zeros in a matrix?

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P_M_Cap
P_M_Cap 2022-2-14
编辑： Simon Dengler 2022-2-14
Ran in:
hi,
i have a matrix, for example
A=[1 2 3; 4 5 6; 7 8 9]
A = 3×3
1 2 3 4 5 6 7 8 9
how can i add a first row of zeros and a first colum of zeros to reach the following results?
B=[0 0 0 0; 0 1 2 3; 0 4 5 6; 0 7 8 9]
B = 4×4
0 0 0 0 0 1 2 3 0 4 5 6 0 7 8 9
and how can i delete the last row and the last column of a matrix to reach this second results?
C=[0 0 0; 0 1 2; 0 4 5]
C = 3×3
0 0 0 0 1 2 0 4 5
thank you very much matlab users!

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采纳的回答

Arif Hoq
Arif Hoq 2022-2-14
Ran in:
A=[1 2 3; 4 5 6; 7 8 9];
AA=[zeros(1,3);A];
AAA=zeros(4,1);
B=[AAA AA];
B(:,end)=[];
B(end,:)=[]
B = 3×3
0 0 0 0 1 2 0 4 5

更多回答（2 个）

Star Strider
Star Strider 2022-2-14
Ran in:
The easiest way is to create an appropriate zeros matrix and just index into it —
A=[1 2 3; 4 5 6; 7 8 9];
B = zeros(size(A,1)+1,size(A,2)+1);
B(2:end,2:end) = A
B = 4×4
0 0 0 0 0 1 2 3 0 4 5 6 0 7 8 9
C = B(1:end-1,1:end-1)
C = 3×3
0 0 0 0 1 2 0 4 5
Four lines of code to do everything!
.
Simon Dengler
Simon Dengler 2022-2-14
编辑：Simon Dengler 2022-2-14
Ran in:
bit more general and faster?
A=[1 2 3; 4 5 6; 7 8 9];
A = 3×3
1 2 3 4 5 6 7 8 9
B=zeros(size(A)+1);
B(2:end,2:end)=A
B = 4×4
0 0 0 0 0 1 2 3 0 4 5 6 0 7 8 9

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