program corcoef
      implicit none
      real*8 as,sx,sy,sxy,sx2,sy2,x,y,cc
      integer*4 i,N,M,iargc
      character*80 f1,f2,st
      if(iargc().eq.0)then
      write(6,9)
9     format(' Correlate Nth column in file1 with Mth column of file2',
     1/,/,' file1: ',$)
      read(5,'(a)')f1
      write(6,91)
91    format(' file2: ',$)
      read(5,'(a)')f2
      write(6,92)
92    format(' N M: ',$)
      read(5,*)N,M
      else
      call getarg(1,f1)
      call getarg(2,f2)
      call getarg(3,st)
      read(st,*)N
      call getarg(4,st)
      read(st,*)M
      endif
      as=0.0d0
      sxy=0.0d0
      sx2=0.0d0
      sy2=0.0d0
      sx=0.0d0
      sy=0.0d0
      open(9 ,file=f1)
      open(91,file=f2)
1     read(9 ,*,end=99,err=99)(x,i=1,N)
      read(91,*,end=99,err=99)(y,i=1,M)
      as=as+1.0d0
      sx=sx+x
      sy=sy+y
      sx2=sx2+x**2
      sy2=sy2+y**2
      sxy=sxy+x*y
      goto 1
99    close(9)
      close(9)
      write(6,*)int(as),' points'
      if(as.gt.0.0d0)then
       cc=(as*sxy-sx*sy)/dsqrt(as*sx2-sx**2)/dsqrt(as*sy2-sy**2)
       write(6,8)cc
8      format(' Correlation coefficient = ',f10.5)
      endif
      stop
      end