from java.awt import Color
from jhplot import *
from java.lang.Math import *
from org.apache.commons.math3.special.Erf import *

"""
Crystal Ball function as described in http://en.wikipedia.org/wiki/Crystal_Ball_function
"""

class MyFunc(FNon):
      def value(self, x):
                xmean=self.p[0]
                sigma= self.p[1]
                n = int(self.p[2])
                alpha=self.p[3]
                s=(x[0] - xmean) / sigma
                A=pow( (n / abs(alpha)), n) * exp(-0.5*abs(alpha)*abs(alpha))
                B= (n /  abs(alpha)) -  abs(alpha)
                C=(n/abs(alpha)) * (1.0/(n-1)) * exp(-0.5*abs(alpha)*abs(alpha))
                D=sqrt(3.14/2) * (1 +  erf(abs(alpha)/1.4))
                N=1.0/(sigma*(C+D))
                if s> -alpha:
                     return N*exp( -0.5*s*s );
                if s<= -alpha:
                     return N*A*pow((B-s), -n);

c1 = HPlot()
c1.visible();   c1.setAutoRange()
pl = MyFunc("Crystal Ball function",1,4)
pl.setParameters([0.0,1.0,3,1.0])
print pl.value([0.4])
f1=F1D(pl,-10,4)
c1.draw(f1)