C**********************************************************************
      function erf(x)
c**********************************************************************

c     + + + PURPOSE + + +
c     For the equation Y = erf(X), the function returns Y, given X
c     written by L. Hagen and coded by I. Elmanyawi.

c     + + + ARGUMENT DECLARATIONS + + +

c     + + + LOCAL VARIABLES + + +
      real erf
      real x, a,b,c,d,e,f,g,h,i,j,k, x2, x3, x4, x5, z
c
c     + + + END SPECIFICATIONS + + +
c
      a = -0.000018936
      b =  0.030284321
      c =  1.12891921
      d =  0.37693092
      e =  0.029375235
      f =  0.088848989
      g =  0.068200064
      h =  0.022155958
      i =  0.050754183
      j =  0.038090749
      k =  0.034275052

      z = x
      x = abs(x)
      x2= x*x
      x3= x2*x
      x4= x3*x
      x5= x4*x

      erf= (a + c*x + e*x2 + g*x3 + i*x4 + k*x5)/
     &      (1.000000 + b*x + d*x2 + f*x3 + h*x4 + j*x5)
      erf = erf * z / x
      return
      end