FUNCTION SOMB,X,Y
;+
; Z=SOMB(X,Y)
; Computes the sombrero function for the arrays X and Y,
; See Gaskill, page 72. NOTE: Gaskill uses the radius R
; as the input. This function uses the rectulangular arrays
; X and Y. Internally, R is computed from X and Y.
;
; X and Y must be arrays that are of the same size.
;
; USAGE
; Compute X and Y arrays using MESHDOM
; s=FINDGEN(101)/10 -5
; t=FINDGEN(101)/10 -5
; MESHDOM,s,t,X,Y
; Z=SOMB(X/2,Y/3)
; SURFACE,Z,X/2,Y/3
;
; HISTORY
; Written by Harvey Rhody, September 1997
;-

R=SQRT(X^2+Y^2)
Z=0.*X
I0=WHERE(R EQ 0.)
IF MIN(I0) GE 0 THEN Z(I0)=1.0
I1=WHERE(R NE 0.)
Z(I1)=2*BESELJ(!PI*R(I1),1)/(!PI*R(I1))
RETURN,Z
END