Normalizing a list of numbers in Python

Question

I need to normalize a list of values to fit in a probability distribution  i e  between 0 0 and 1 0   I understand how to normalize  but was curious if Python had a function to automate this   I d like to go from   raw    0 07  0 14  0 07      to    normed    0 25  0 50  0 25

User · Accepted Answer

Use     norm    float i  sum raw  for i in raw    to normalize against the sum to ensure that the sum is always 1 0  or as close to as possible    use   norm    float i  max raw  for i in raw    to normalize against the maximum

User · Answer

if your list has negative numbers  this is how you would normalize it  a   range -30 31 5  norm     float i -min a    max a -min a   for i in a

User · Answer

For ones who wanna use scikit-learn  you can use from sklearn preprocessing import normalize  x    1 2 3 4  normalize  x     array   0 18257419  0 36514837  0 54772256  0 73029674    normalize  x   norm  quot l1 quot     array   0 1  0 2  0 3  0 4    normalize  x   norm  quot max quot     array   0 25  0 5   0 75  1

User · Answer

If working with data  many times pandas is the simple key  This particular code will put the raw into one column  then normalize by column per row   But we can put it into a row and do it by row per column  too  Just have to change the axis values where 0 is for row and 1 is for column    import pandas as pd   raw    0 07  0 14  0 07     raw df   pd DataFrame raw  normed df   raw df div raw df sum axis 0   axis 1  normed df   where normed df will display like       0 0   0 25 1   0 50 2   0 25   and then can keep playing with the data  too

User · Answer

try   normed    i sum raw  for i in raw   normed  0 25  0 5  0 25

User · Answer

How long is the list you re going to normalize   def psum it        This function makes explicit how many calls to sum   are done       print  Another call       return sum it   raw    0 07 0 14 0 07  print  How many calls to sum     print   r psum raw  for r in raw   print   nAnd now   s   psum raw  print   r s for r in raw     if one doesn t want auxiliary variables  it can be done inside   a list comprehension  but in my opinion it s quite Baroque     print   nAnd now   print   r s  for s in  psum raw   for r in raw    Output    How many calls to sum      Another call    Another call    Another call     0 25  0 5  0 25       And now    Another call     0 25  0 5  0 25       And now    Another call     0 25  0 5  0 25

User · Answer

Try this     from   future   import division  raw    0 07  0 14  0 07     def norm input list       norm list   list        if isinstance input list  list           sum list   sum input list           for value in input list              tmp   value   sum list             norm list append tmp        return norm list  print norm raw    This will do what you asked  But I will suggest to try Min-Max normalization   min-max normalization     def min max norm dataset       if isinstance dataset  list           norm list   list           min value   min dataset          max value   max dataset           for value in dataset              tmp    value - min value     max value - min value              norm list append tmp       return norm list

User · Answer

There isn t any function in the standard library  to my knowledge  that will do it  but there are absolutely modules out there which have such functions   However  its easy enough that you can just write your own function   def normalize lst       s   sum lst      return map lambda x  float x  s  lst    Sample output    gt  gt  gt  normed   normalize raw   gt  gt  gt  normed  0 25  0 5  0 25

User · Answer

If you consider using numpy  you can get a faster solution   import random  time import numpy as np  a   random sample range 1  20000   10000  since   time time    b    i sum a  for i in a   print time time  -since    0 7956490516662598  since   time time    c np array a  d c sum a   print time time  -since    0 001413106918334961

User · Answer

Use scikit-learn  from sklearn preprocessing import MinMaxScaler data   np array  1 2 3   reshape -1  1  scaler   MinMaxScaler   scaler fit data  print scaler transform data

[python] Normalizing a list of numbers in Python

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