Fill a border of a matrix with 0's

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Jhangir
Jhangir 2013-11-6
编辑： Image Analyst 2013-11-6
Lets say I have a matrix A. I want to replace all the values at the border meaning, the first row, the last row, the first column, and the last column with 0s, How do I do this

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Image Analyst
Image Analyst 2013-11-6
Try this:
grayImage(1,:) = 0;
grayImage(end,:) = 0;
grayImage(:,1) = 0;
grayImage(:,end) = 0;
Related, if you want to add a layer of 0's all the way around, you can use padarray() if you have the Image Processing Toolbox:
paddedImage = padarray(grayImage,[1 1]);
  2 个评论
Jhangir
Jhangir 2013-11-6
[n,m]=size(R);
R(1,:)=0;,R(n,:)=0;,R(:,1)=0;,R(:,m)=0;
I just did this I think it worked
Image Analyst
Image Analyst 2013-11-6
编辑：Image Analyst 2013-11-6
Like I showed you "end" is a convenient way to get the last index of any dimension without actually having to use the size() function to determine what index value that would be.
And you don't need the commas in your code. For readability I're recommend putting them on separate lines.

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