pro box_car,dat,npts,dat_av,dat_sd,dat_sdom

;--------------------------------------------------------------
;  smooth a series of data over +/- npts points,   compute
;  the mean and the standard deviation.
;
; Input:
;    dat.........the data to be smoothed, must be a series (vector)
;    npts........smooth over +/- npts,  the total # of points in the stats will be npts*2+1
;
; Output:
;    dat_av......averages
;    dat_sd......standard deviation
;    dat_sdom....standard deviation of the mean (Std. Dev. / sqrt(n))
;
;  source: Mark Hervig, GATS Inc.
;--------------------------------------------------------------

   nrec  = n_elements(dat)   
   npts  = long(npts)
   
   dat_av   = dat ;* 0.
   dat_sd   = dat * 0.
   dat_sdom = dat * 0.

   for i = 0L+npts,nrec-1L-npts do begin
   
     dat_av(i) = mean(   dat(i-npts:i+npts))
     
     dat_sd(i) = stddev( dat(i-npts:i+npts))
     
     dat_sdom(i) = stddev( dat(i-npts:i+npts)) / sqrt(2*npts)
     
   endfor
   
   return
   end