Replace erf to erfc by importing the func

Author: bobleesj

Diff for: src/diffpy/srfit/pdf/characteristicfunctions.py

@@ -41,7 +41,7 @@
 from numpy import arctanh as atanh
 from numpy import ceil, exp, log, log2, pi, sign, sqrt
 from numpy.fft import fftfreq, ifft
-from scipy.special import erf
+from scipy.special import erfc
 
 from diffpy.srfit.fitbase.calculator import Calculator
 
@@ -198,8 +198,6 @@ def lognormalSphericalCF(r, psize, psig):
     if psig <= 0:
         return sphericalCF(r, psize)
 
-    erfc = lambda x: 1.0 - erf(x)
-
     sqrt2 = sqrt(2.0)
     s = sqrt(log(psig * psig / (1.0 * psize * psize) + 1))
     mu = log(psize) - s * s / 2