FUNCTION nndist,x,y
;
;Nearest-neighbour distance.
;Having in X,Y (1D input arrays with equal length) 2D coordinates
;representing objects, the routine calculates for each object
;the distance to its nearest object.
;The resulting FLOAT array is of the same length like X,Y.
;
;EXAMPLE:  result = NNDIST(x,y)
;
;14 September 2004, Michal

on_error,1
six=size(x)
siy=size(y)
if (six(0) ne 1) or (siy(0) ne 1) then message,'Input arrays must be 1D'
if six(1) ne siy(1) then message,'Input arrays must have equal size'
if six(2) ne siy(2) then message,'Input arrays must be of equal type'
if six(1) lt 2 then message,'Only one object in input arrays'
n=six(1)

;Loop over objects

out=fltarr(n)
for i=0,n-1 do begin
   di=sqrt(float((x-x(i))^2+(y-y(i))^2))	;calculate distances
   di=di(where(di))				;eliminate zero distance
   out(i)=min(di)				;find minimum distance
endfor

RETURN,out

END