FUNCTION DIAG,v,n
;+
;A=diag(v) constructs a diagonal matrix with the vector
;v as the diagonal.
;
;A=diag(v,n) constructs a diagonal matrix of size nxn
;using the first n elements of v if n<n_elements(v) and filling
;the diagonal with zeros if n>n_elements(v).
;
;Note: Kept for old programs. It is better to use the built-in
;DIAG_MATRIX program in IDL.
;
;Harvey Rhody
;May 18, 2002
;-

nv=n_elements(v)
IF n_params() LT 2 THEN n=nv
type=Size(V,/type)
A=Make_Array(n,n,TYPE=type)
nd=n<nv
k=(n+1)*findgen(nd)
A[k]=v[0:nd-1]
Return,A
END