central_limit.py

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#!/usr/bin/env python

import sys, os
from os.path import join
from HandyFuncs import MakeGradient

if "PYTHONSTARTUP" in os.environ:
    if sys.argv[0]:
        execfile(os.environ["PYTHONSTARTUP"])
elif os.path.exists("rootlogon.py"):
    execfile("rootlogon.py")


#colors = [ kRed, kBlue, kGreen+2, kMagenta, kCyan ]
#Nexps = [ 2, 3, 4, 5, 6, , 30, 50 ]
Nexps = range(2, 31)
colors = MakeGradient( len(Nexps), (1, 0, 0), (0, 0, 1) )
trials = 10000

rand = TRandom3()

hists = {}


for nexp in Nexps:
    hists[nexp] = TH1D("h%i"%nexp, ";Mean;", 101, 0, 1.01)
    for t in range(trials):
        sum = 0
        for i in range(nexp):
            sum += rand.Integer(2)
        mean = float(sum) / float(nexp)
        hists[nexp].Fill(mean)


fits = {}

c1 = TCanvas("c1","c1")

opt = "hist"

gStyle.SetOptFit(False)

for nexp, color in zip(Nexps, colors):
    hists[nexp].SetLineColor(color)
    hists[nexp].Fit("gaus")
    fits[nexp] = hists[nexp].FindObject("gaus")
    fits[nexp].SetLineColor(color)
    hists[nexp].Draw(opt)
    fits[nexp].Draw("same")
    
    #if "same" not in opt:
    #    opt += "same"
    l1 = TLatex(0.3, 0.5, "%s"%nexp)
    l1.SetNDC()
    l1.SetTextColor(color)
    l1.SetTextSize(0.07)
    l1.Draw()
    c1.Print("clt_%i.png"%nexp)