subroutine  csrotf (n,cx,incx,cy,incy,c,s)
c
c     applies a plane rotation, where the cos and sin (c and s) are real
c     and the vectors cx and cy are complex.
c     jack dongarra, linpack, 3/11/78.
c
      complex cx(1),cy(1),ctemp
      real 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
        ctemp = c*cx(ix) + s*cy(iy)
        cy(iy) = c*cy(iy) - s*cx(ix)
        cx(ix) = ctemp
        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
        ctemp = c*cx(i) + s*cy(i)
        cy(i) = c*cy(i) - s*cx(i)
        cx(i) = ctemp
   30 continue
      return
      end