Create a 2d array with 1 on the border and 0 inside

Question

I am puzzled with the following. How can I create a, e.g., 10x10 array A[i,j] where the border is filled with 1's and the rest of the elements are 0?

Thanks

This and more: 21286, if anyone finds a better duplicate, let me know and I can add it to the list on top. — Kuba, Apr 08 '17 at 11:19
@J.M. BoxMatrix creates a matrix that is (2r+1)x(2r+1). There is no way to select r such that the dimension of the matrix is 10x10. — C. E., Apr 08 '17 at 15:28
@Kuba I voted to close this as "easily found in the documentation" because I believe that it has been sufficiently answered here, and that this question is more limited in scope than the proposed duplicate. I wrote an answer for easy reference should someone find this in the future. — C. E., Apr 08 '17 at 15:30

C. E. · Accepted Answer · 2017-04-08T18:11:08.313

6

Kuba suggested

ArrayPad[ConstantArray[0, {8, 8}], 1, 1]

Similarly, you can do this:

CenterArray[ConstantArray[0, {8, 8}], {10, 10}, 1]

J.M. proposed the following:

1 - BoxMatrix[3, {10, 10}]

One may also use

SparseArray[{{1, _} -> 1, {_, 1} -> 1, {-1, _} -> 1, {_, -1} -> 1}, {10, 10}]

Normal can be used if an explicit (rather than a sparse) array is desired.

edited Apr 08 '17 at 18:11

answered Apr 08 '17 at 15:28

C. E.

1 Answers1