def chain_binomial_monte_carlo(beta, gamma, num_sims, num_metro_zeros, num_child_zeros, num_adult_zeros):
# run many (num_sims) instances of chain binomial simulation and return average epidemic size    

    #d_metropop, metro_ids = pop_func.import_metropop(filename_metropop, 2, 3)
    population_size = sum([d_metropop[x] for x in metro_ids])
    threshold = 0.10 # 10% of population size is our threshold for a large epidemic

    d_metro_age_pop = pop_func.calc_metro_age_pop(filename_metropop, alpha)

    large_epidemic_sizes= [] # will keep list of outbreak sizes that are large epidemics
    for sim in range(1,num_sims):
        incidence_time_series, outbreak_size = chain_binomial_one_simulation(d_metro_age_pop, metro_ids, beta, gamma, air_network, num_metro_zeros, num_child_zeros, num_adult_zeros, C)
        # Note we are not using the incidence time series right now
        
        # figure out if this is small outbreak or large epidemic
        if outbreak_size > threshold * population_size: # if outbreak reached more than 10% of the population
            
            # call it a large epidemic and save its size
            large_epidemic_sizes.append(outbreak_size)
            
    # calculate average large epidemic size, and how frequent they were
    if large_epidemic_sizes:
        average_epidemic_size = np.mean(large_epidemic_sizes)/float(population_size)
        probability_epidemic = len(large_epidemic_sizes)/float(num_sims)
    else:
        average_epidemic_size = 0
        probability_epidemic = 0
    
    
    return average_epidemic_size
dict_popdata, ages, years = pop_func.import_popdata(us_popdata, 0, 1, 2)
dict_childpop, dict_adultpop = pop_func.pop_child_adult (dict_popdata, years)

# READ Germany contact data
#filename_germ_contact_data = 'Dropbox/Anne_Bansal_lab/Contact_Data/polymod_germany_contact_matrix_Mossong_2008.csv'
filename_germ_within_group_contact_data = 'Dropbox/Anne_Bansal_lab/Contact_Data/within_group_polymod_germany_contact_matrix_Mossong_2008.csv'
filename_germ_all_contact_data = 'Dropbox/Anne_Bansal_lab/Contact_Data/all_ages_polymod_germany_contact_matrix_Mossong_2008.csv'

# READ Germany population data
filename_germ_pop_data = 'Dropbox/Anne_Bansal_lab/UNdata_Export_2008_Germany_Population.csv'
   
     
# DEFINE POPULATION PARAMETERS
year = 2010
alpha = pop_func.calc_alpha(year, dict_childpop, dict_adultpop)
d_metro_age_pop = pop_func.calc_metro_age_pop(filename_metropop, alpha)
ch_travelers_r = 0.0 # fraction of children who travel
ad_travelers_s = 1

# CONTACT MATRIX
q_c, q_a, p_c, p_a, _, _ = pop_func.calc_p(filename_germ_within_group_contact_data, filename_germ_pop_data, filename_germ_all_contact_data)
C = pop_func.calc_contact_matrix_pqa(p_c, p_a, q_c, q_a, alpha)
#print C
                        
# DEFINE DISEASE PARAMETERS
R0 = 1.2
gamma = 0.5 # recovery rate based on (1/gamma) day infectious period
### UNIT TEST ###
unit_test = 'no_trans'
#  NO TRANSMISSION #
#BETA = 0