*****************************************************************************
* PROGRAM:     access1.f - Sample program to read crsp daily and monthly stock 
*                         files using random access programming
*
* DESCRIPTION: This program calculates beta in a given calender range
*
*              All securities with data in the monthly and daily databases
*
* USAGE:       Change udopen to umopen and udclose to umclose for monthly 
*              data where specified.
*
*              Add code for desired extraction or processing where 
*              specified.  See the "Stock File User's Guide" and "Stock
*              File Programmer's Guide" for assistance. 
*
*          Then, compile the program as follows: f77 -o access access1.f -I$CRSP_INCLUDE $CRSP_LIB/crsplib.a
*
*              Then run the executable "access" generated from the compile
*              step by simply typing:  access
*              
****************************************************************************

      program access

      include 'us.txt'

      integer kperm

      integer begdate,enddate,bind,eind

c------------------------------------------------------------------------
c Required beginning dates and ending dates are initialized here

      data begdate,enddate /19500101, 19591231/

c-----------------------------------------------------------------------------
c This statement opens the monthly index data

      call umcal(nyseamex)

c This statement opens the monthly data file for NYSE and AMEX

      call umopen(nyseamex)
c-----------------------------------------------------------------------------

c-----------------------------------------------------------------------------
c If you know the CRSP permanent id numbers "permno" use the following 
c lines of code to read the file. For every number "kperm" in the file,
c the machine will look for the corresponding data on the disk (and
c eliminate the "c" in the first column)

c 100 read (10,1000,end=900) kperm
c1000 format(i5) 

c      call usgetper(1,kperm,infos+returns,*900)   

c If the machine could not find this number, go to the next one

c      if (kperm. ne . permno) goto 100
c----------------------------------------------------------------------------
c Otherwise, if you just want to go through all the data, use the
c following

  100 call usgetper(1,inext,none,*900)

c Now check to see whether this security has data in the range you
c are interested in -- if not, go back to 100 and get another one!
 
      if(caldt(enddat).lt.begdate.or.caldt(begdat).gt.enddate) goto 100

c We now have the required information available. Calculate beta!
      
      call usgetper(1,isame,infos+returns,*900)

c---------------------------------------------------------------------------
c Now process the data (in this case, compute beta)

      call mysub(permno,compnm(numnam),ret,begret,endret,vwretd)
 

c----------------------------------------------------------------------------
c now go get data for another company

      goto 100                               


c-----------------------------------------------------------------------------
  900 call umclose
c-----------------------------------------------------------------------------

      close(unit=10)
      close(unit=11)

      stop
      end

      subroutine mysub(permno,comp,ret,begret,endret,mkt)
      real ret(1),mkt(1)
      integer permno,begret,endret
      character*32 comp
      x=0
      y=0
      x2=0
      y2=0
      xy=0
      t=0
      do 23000 i = begret,endret 
         if(.not.(ret(i) .ge. -1))goto 23002
            if(.not.( i .gt. begret))goto 23004
               if(.not.( ret(i-1) .ge. -1))goto 23006
                  t=t+1
                  x = x + mkt(i)
                  y = y + ret(i)
                  x2 = x2 + mkt(i) * mkt(i)
                  y2 = y2 + ret(i) * ret(i)
                  xy = xy + mkt(i) * ret(i)
23006          continue
23004       continue
23002    continue
23000    continue
      if(.not.(t .gt. 0 ))goto 23008
         x = x/t
         y = y/t
         x2 = x2 - t*x*x
         xy = xy - t*x*y
         beta = xy/x2
         goto 23009
c     else
23008    continue
         beta = -999999 
23009 continue
      write(6,*)permno,' ',comp,beta
      end