Given a matrix M, row vector v of appropriate length, and diagonal index d (where 0 indicates the main diagonal and off-diagonals are identified by positive and negative integers), return a new matrix where the specified diagonal of M is replaced by v. You may assume that v is the correct length for the specified diagonal. If d is not provided, assume it is zero.

For example,

M = magic(5);
setDiagonal(M,1:4,-1)

ans =
  17    24     1     8    15
   1     5     7    14    16
   4     2    13    20    22
  10    12     3    21     3
  11    18    25     4     9