function tbl = Dif(y)
% usage: DividDif(y)
% description: for input vector y of ordinates of function f(x)
% returns a zero padded matrix whose ith row is the ith diagonal
% of a difference table for the data.

n = length(y);
y = y(:); % make y column
tbl = zeros(n,n);
tbl(:,1) = y(:);
for k = (2:n)
  tbl(1:n-k+1,k) = (tbl(2:n-k+2,k-1)-tbl(1:n-k+1,k-1));
end;