# program to fix up histogram (normalization, etc) and 
 #  prepare plots with both histogram and the analytical PDF
 # called AFTER a call to 'run'
mkhist := proc(lambda, n_mea, n_smpls_per_mea)
 #
global xacc, hist, bin_range, bin_size, n_bins, midpt, phi, pex;
local histnorm_inv, bi, hi, exact_pdf;
 #
 # normalize histogram (histnorm_inv is INVERSE of normalization):
histnorm_inv := 1.                                :
 #              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ <-- MODIFY -- 
 #                                                     fill in correct form 
 # Note histnorm_inv appears in the following line:
for bi to n_bins do hist[bi] := hist[bi]*histnorm_inv od:
 # plot histogram:    
hi := [[midpt(n),hist[n]] $n=1..n_bins]:
phi := plot(hi,x=0..bin_range+bin_size,style=point,symbol=circle,color=red):
 # plot exact probability density function
exact_pdf := proc(x)
    global lambda;
    exp(-x/lambda)/lambda:
end:
pex := plot(exact_pdf(x),x=0..bin_range+bin_size,style=line,color=blue):

end: