def p2chi(a,df,guess=128.,ld=0): if abs(chi2p(guess,df)-a)>0.00001: if chi2p(guess,df): if ld==0: ld = guess/2. else: ld = ld/2. guess -= ld p2chi(a,df,guess,ld) else: if ld==0: ld = guess/2. else: ld = ld/2. guess += ld p2chi(a,df,guess,ld) else: return guess