#plotDist(f,x,K): Given a prob. gen. function f(x) that has a 
#Taylor series
#for a discrete r.v.
#plots its normalized version (X-mu)/sig between mu-K1*sig and
#mu+K2*sig
#For example, try:
#plotDist((1+x)^40,x,5,5);
plotDist:=proc(f,x,K1,K2) local mu,f1,lu,gu,sig,i,j1:
f1:=f/subs(x=1,f):
mu:=subs(x=1,diff(f1,x)):
gu:=f1/x^mu:
sig:=sqrt(subs(x=1,x*diff(x*diff(gu,x),x))):

lu:=taylor(f1,x=0,trunc(mu)+K2*trunc(sig)+10):

lu:=[seq([i,coeff(lu,x,i)],i=max(0,trunc(mu-K1*sig))..trunc(mu+K2*sig))]:

lu:=evalf([seq([(lu[j1][1]-mu)/sig,lu[j1][2]*sig],j1=1..nops(lu))]):

plot(lu,scaling=constrained):

end: