      subroutine srotf (n,sx,incx,sy,incy,c,s)
c
c     applies a plane rotation.
c     jack dongarra, linpack, 3/11/78.
c     modified 12/3/93, array(1) declarations changed to array(*)
c
      real sx(*),sy(*),stemp,c,s
      integer i,incx,incy,ix,iy,n
c
      if(n.le.0)return
      if(incx.eq.1.and.incy.eq.1)go to 20
c
c       code for unequal increments or equal increments not equal
c         to 1
c
      ix = 1
      iy = 1
      if(incx.lt.0)ix = (-n+1)*incx + 1
      if(incy.lt.0)iy = (-n+1)*incy + 1
      do 10 i = 1,n
        stemp = c*sx(ix) + s*sy(iy)
        sy(iy) = c*sy(iy) - s*sx(ix)
        sx(ix) = stemp
        ix = ix + incx
        iy = iy + incy
   10 continue
      return
c
c       code for both increments equal to 1
c
   20 do 30 i = 1,n
        stemp = c*sx(i) + s*sy(i)
        sy(i) = c*sy(i) - s*sx(i)
        sx(i) = stemp
   30 continue
      return
      end
