REAL FUNCTION echisterr(lunit,icoll,rc)
*
* Calculate statistical errors for exponential-weighted running sum of
* collector charges for purposes of RC filtering.
* These errors are very correlated point-to-point because
* they sum over many of the same uncorrelated time bins.
*
* PAW imposes an output record length limit of 132 characters.
*
* 19 May 2014 2013 J.A.Crittenden
*
      REAL
     +T       ,DELT    ,QDENS   ,GRID    ,COL1    ,COL2    ,
     +COL3    ,COL4    ,COL5    ,COL6    ,COL7    ,COL8    ,
     +COL9    ,COL10   ,COL11   ,COL12   ,COL13   ,COL14   ,
     +COL15   ,COL16   ,COL17    
*
      LOGICAL         CHAIN
      CHARACTER*128   CFILE
*
      COMMON /PAWCHN/ CHAIN, NCHEVT, ICHEVT
      COMMON /PAWCHC/ CFILE
*
      COMMON/PAWIDN/IDNEVT,OBS(13),
     +T       ,DELT    ,QDENS   ,GRID    ,COL1    ,COL2    ,
     +COL3    ,COL4    ,COL5    ,COL6    ,COL7    ,COL8    ,
     +COL9    ,COL10   ,COL11   ,COL12   ,COL13   ,COL14   ,
     +COL15   ,COL16   ,COL17    
*
* Unit number of output file
      integer lunit
* RC time constant (seconds)
      real rc
* Collector number
      integer icoll
* Time range
      vector tlims
* Filter weight
      real wt,wtsum
*
      real tmin, tmax
*
      real qe(500000,17)
      real t0(500000)
      real qqe(17)
*
      tmin=tlims(1)*1e-9
      tmax=tlims(2)*1e-9
*
* Limit calculation to restricted time range
* 23 July 2012 JAC
      if ( t .gt. tmax ) goto 900
*
      qe(idnevt,1)=col1
      qe(idnevt,2)=col2
      qe(idnevt,3)=col3
      qe(idnevt,4)=col4
      qe(idnevt,5)=col5
      qe(idnevt,6)=col6
      qe(idnevt,7)=col7
      qe(idnevt,8)=col8
      qe(idnevt,9)=col9
      qe(idnevt,10)=col10
      qe(idnevt,11)=col11
      qe(idnevt,12)=col12
      qe(idnevt,13)=col13
      qe(idnevt,14)=col14
      qe(idnevt,15)=col15
      qe(idnevt,16)=col16
      qe(idnevt,17)=col17

      t0(idnevt) = t

* Limit calculation to restricted time range
* 23 July 2012 JAC
      if ( t .lt. tmin ) goto 900
*
      if(idnevt.gt.1) then

         do i=1,17
            qqe(i)=0.
         enddo
*---------------------------------------------------------
* Reduce summed time interval to five RC decay times
* 12 July 2013 JAC
         i00=1
         do ii=idnevt-1,1,-1
           if ( t-t0(ii) .gt. 5*rc )then
              i00=ii
              goto 100
           endif
         enddo
 100     continue
*         if( t0(i00) .ge. (tmin-10*rc) ) then
*           print *,idnevt,t,i00,t0(i00),tmin,tmax
*          do i=1,17
           do i=icoll,icoll
*            do j=1,idnevt-1
             wtsum = 0.
             do j=i00,idnevt-1

               if(j.eq.1)then
* First-bin time value is its width
                 wt=((t0(j))/rc)*exp(-(t-t0(j))/rc)
                 qqe(i) = qqe(i) +  wt*qe(j,i)**2
                 wtsum = wtsum+wt
               else
* Protect against simultaneous entries. Exclude them from sum.
                 if(t.gt.t0(j))then
                   wt=((t0(j)-t0(j-1))/rc)*exp(-(t-t0(j))/rc)
                   qqe(i) = qqe(i) +  wt*qe(j,i)**2
                   wtsum = wtsum+wt
*                   write(*,1100)
*     &             j,i00,idnevt,t,t0(j),qe(j,i),wtsum,exp(-(t-t0(j))/rc)
 1100              format(3i8,4(2x,e12.5))
                 endif
               endif

             enddo
             if (wtsum.gt.0)then
                qqe(i) = qqe(i) / wtsum
                qqe(i) = sqrt ( qqe(i) )
             else
                qqe(i) = 0.
             endif

           enddo
* Write output record
*           write(*,2000)t,delt,(qqe(k),k=1,1)
           write(lunit,2000)t,delt,(qqe(k),k=1,9)
 2000      format(11(e12.5,1x))

*         endif 

*         if(idnevt.le.5) then
*            write(*,1000)'Rtn ECHISTERR event: ',idnevt,
*     &                   '  Collector ',icoll,
*     &                   '  RC = ',rc,
*     &                   '  TMIN,TMAX=',tmin,tmax

 1000       format(a,i3,a,i3,a,e9.4,a,e9.4,1x,e9.4)
*            write(*,2000)t,delt,qdens,grid,
*     &                   (qqe(k),k=1,9)
*         endif

      endif

 900  continue
*
      echisterr=1.
      END