cesco escreveu:
> I have to generate a list of N random numbers (integer) whose sum is
> equal to M. If, for example, I have to generate 5 random numbers whose
> sum is 50 a possible solution could be [3, 11, 7, 22, 7]. Is there a
> simple pattern or function in Python to accomplish that?
>
> Thanks and regards
> Francesco
>
May be this is what you want ...
I didn't test it enough ... but seems fine.
from random import randint,shuffle
def GenRInt(m,n):
"""Generate m positive ints whose sum is n"""
# Generate a random list
xl=[randint(1,n-m+1) for i in xrange(m)]
s=sum(xl)
if s==n: return xl
# Adjust each value to make sum==n
xl=[max(x*n/s,1) for x in xl]
s=sum(xl)
if s!=n:
# Compensate for truncations
if s>n:
# s>n is supposed not to occur. Just in case ...
ixs=filter(lambda x: xl[x]>1,range(m))
shuffle(ixs)
for i in ixs[:s-n]: xl[i]-=1
else:
ixs=range(m)
shuffle(ixs)
for i in ixs[:n-s]: xl[i]+=1
return xl
# Test it ...
xl=GenRInt(10,50)
print xl,"->",sum(xl)
print
xl=GenRInt(100,10000)
print xl,"->",sum(xl)
print
xl=GenRInt(1000,1000)
print xl,"->",sum(xl)
Regards.
Paulo
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