Fill a border of a matrix with 0's

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

Answer 1

[Image Analyst]

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]);

[Jhangir]

[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]

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.