# how to make zero padding?

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sheno39 on 8 Oct 2013
Commented: Image Analyst on 5 Apr 2016
can anyone help me to make zero padding for a 4x3 matrix. i have to add a row of zeros in the top,bottom, left and right side of the matrix

Image Analyst on 8 Oct 2013
If you have the Image Processing Toolbox, you can use padarray().
##### 2 CommentsShowHide 1 older comment
Jie on 9 Oct 2013
cool

Slim Ben Ghalba on 21 Nov 2013
a smarter and simpler way. here is an example for zero-padding with 4:
>> a=zeros(1,12)
a =
0 0 0 0 0 0 0 0 0 0 0 0
>> a(1:4:end)=1
a =
1 0 0 0 1 0 0 0 1 0 0 0
Image Analyst on 15 Jul 2014
This does not wrap the matrix with a layer of zeros on all sides like the original poster asked or like padarray() does.

cr on 8 Oct 2013
Edited: cr on 8 Oct 2013
m = [zeros(1,size(m,2)+2); [zeros(size(m,1),1), m, zeros(size(m,1),1)]; zeros(1,size(m,2)+2)];
or even simpler, but needs creating a temp variable:
tmp = zeros(size(m)+2);
tmp(2:end-1,2:end-1) = m;
m = tmp;
Cheers.

Jie on 8 Oct 2013
Edited: Jie on 8 Oct 2013
% just wish you matrix size is not too large
[n m]=size(in_put);
A=['a' 'b' 'c' 'd' 'e' 'f' 'g' 'h' 'i' 'j' 'k' 'l' 'm' 'n' 'o' ];
B=1:20;
str1=[A(m+2), num2str(B(n+2))];
str2=['b2:' A(m+1), num2str(B(n+1))];
str3=['a1:' str1];
out_put(isnan(out_put))=0;
could take some time, but save much effort regarding the mat size. I think the string part could be optimized somehow, but i just don't know how. Also u can try some simple but boring methods. like
a(1,2:end-1)=ones(1,size(a,2)-1)
or the alike.

Jos (10584) on 8 Oct 2013
Edited: Jos (10584) on 8 Oct 2013
Pad a matrix M with N zeros to all sides using indexing (neither trivial nor boring):
M = ceil(10*rand(3,4))
N = 2
if N > 0
M(end+2*N,end+2*N) = 0
M = M([end-N+1:end 1:end-N], [end-N+1:end 1:end-N])
end
If you have the image toolbox, take a look at PADARRAY.

FRANCISCO JAVIER on 8 Oct 2013
M=rand(2,1);
K=[zeros(2,1) M zeros(2,1)];
N=[zeros(1,3); K; zeros(1,3)];

Kiarash Ahi on 15 Jul 2014
Edited: Kiarash Ahi on 15 Jul 2014
Try this as well:
[M N]=size(k);
for n=1:2:N
k(:,n)=0
end
end

Md. Kamal Hossain on 5 Apr 2016
How to add zero in a sequence
Image Analyst on 5 Apr 2016
If the sequence is stored in a vector, and index is the location where you want to add/insert the zeros:
newVec = [vec(1:index-1), 0, vec(index:end)];