CODEWITHSUNDEEP
pythontypes
Srayan Guhathakurta
Srayan Guhathakurta

Reputation: 556

statistical calculation using lists in Python

I am using Python to implement the following equation:

S[n+1] = (k * S[n]) MOD m The values of the variables are: S[0] = 1111 k = 16807 m = 2147483647 I have calculate 10000 values (so S[0] to S[9999]).

I am using lists to calculate and append the values. This is what I am doing:

# Respective values of k, m and Seed value S[0] in sList
k = 16807
m = 2147483647
sList = [1111]

# Populating the list/array for 10000 iterations
while len(sList) < 10000:
   Sn = (k * sList[-1]) % m
   sList.append(Sn)
print (sList)

While the code works perfectly for smaller values of k and m, I am getting incorrect results S[2] onwards. I manually calculated S[2]=1417880224, however my code is generating S[2] = 297389177.

Is this happening because the numbers I am trying to append in the list is going beyond a certain range? Do I need to type cast to a different data type (like double)? Where am I going wrong?

Upvotes: 0

Views: 52

Answers (1)

Sait
Sait

Reputation: 19825

Let's do it by hand using your definitions with a calculator:

>>> 1111
1111
>>> (16807 * 1111) % 2147483647
18672577
>>> (16807 * 18672577) % 2147483647
297389177

These are the same results your code produces.

So, it seems like either your hand calculations or the recursive formula you are providing is wrong.

Upvotes: 3

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