saving an ordered pair from a list of numbers using python

Question

I have an array of numbers:

q1a = [1,2,2,2,4,3,1,3,3,4,0,0]

I want to save these in an array where it will be stored in as (number, proportion of the number) using PYTHON.

Such as : [[0 0.1667], [1 0.1667], [2 0.25], [3 0.25], [4 0.167]].

This is essential to calculate the distribution of the numbers. How can I do this?

Although I wrote the code to save the numbers as : (number, number of times it occurred in the list) but I cant figure it out how I can find the proportion of each number. Thanks.

sorted_sample_values_of_x = unique, counts = np.unique(q1a, return_counts=True)
np.asarray((unique, counts)).T
np.put(q1a, [0], [0])

sorted_x = np.matrix(sorted_sample_values_of_x)
sorted_x = np.transpose(sorted_x)
print('\n' 'Values of x (sorted):' '\n')
print(sorted_x)

Answer 1

>>> q1a = [1,2,2,2,4,3,1,3,3,4,0,0]
>>> from collections import Counter
>>> sorted([[x, float(y)/len(q1a)] for (x, y) in Counter(q1a).items()],
...        key=lambda x: x[0])
[[0, 0.16666666666666666],
 [1, 0.16666666666666666],
 [2, 0.25],
 [3, 0.25],
 [4, 0.16666666666666666]]

Answer 2

You will need to do two things.

1. Convert sorted_x array as a float array.

2. And then divide it by sum of counts array.

Example -

In [34]: sorted_x = np.matrix(sorted_sample_values_of_x)

In [35]: sorted_x = np.transpose(sorted_x).astype(float)

In [36]: sorted_x
Out[36]:
matrix([[ 0.,  2.],
        [ 1.,  2.],
        [ 2.,  3.],
        [ 3.,  3.],
        [ 4.,  2.]])

In [37]: sorted_x[:,1] = sorted_x[:,1]/counts.sum()

In [38]: sorted_x
Out[38]:
matrix([[ 0.        ,  0.16666667],
        [ 1.        ,  0.16666667],
        [ 2.        ,  0.25      ],
        [ 3.        ,  0.25      ],
        [ 4.        ,  0.16666667]])

To store the numbers with the propertions in a new array, do -

In [41]: sorted_x = np.matrix(sorted_sample_values_of_x)

In [42]: sorted_x = np.transpose(sorted_x).astype(float)

In [43]: ns = sorted_x/np.array([1,counts.sum()])

In [44]: ns
Out[44]:
matrix([[ 0.        ,  0.16666667],
        [ 1.        ,  0.16666667],
        [ 2.        ,  0.25      ],
        [ 3.        ,  0.25      ],
        [ 4.        ,  0.16666667]])

Answer 3

In [12]: from collections import Counter

In [13]: a = [1,2,2,2,4,3,1,3,3,4,0,0]

In [14]: counter = Counter(a)

In [15]: sorted( [ [key, float(counter[key])/len(a)]  for key in counter ] )
Out[15]:
[[0, 0.16666666666666666],
 [1, 0.16666666666666666],
 [2, 0.25],
 [3, 0.25],
 [4, 0.16666666666666666]]

Answer 4

#!/usr/bin/env python
import numpy as np
q1a = [1,2,2,2,4,3,1,3,3,4,0,0]

unique, counts = np.unique(q1a, return_counts=True)
counts = counts.astype(float) # convert to float
counts /= counts.sum()        # counts -> proportion
print(np.c_[unique, counts])

Output

[[ 0.          0.16666667]
 [ 1.          0.16666667]
 [ 2.          0.25      ]
 [ 3.          0.25      ]
 [ 4.          0.16666667]]

Answer 5

As an alternative to collections.Counter , try collections.defaultdict . This allows you to accumulate the total frequency as you proceed through the input (ie should be more efficient) and it's more readable (IMO).

from collections import defaultdict

q1a = [1,2,2,2,4,3,1,3,3,4,0,0]
n = float(len(q1a))
frequencies = defaultdict(int)
for i in q1a:
    frequencies[i] += 1/n

print frequencies.items()
[(0, 0.16666666666666666), (1, 0.16666666666666666), (2, 0.25), (3, 0.25), (4, 0.16666666666666666)]

Answer 6

An fun alternative using numpy

print [(val, 1.*np.sum(q1a==val)/len(q1a) ) for val in np.unique(q1a) ]
#[(0, 0.16666666666666666),
#(1, 0.16666666666666666),
#(2, 0.25),
#(3, 0.25),
#(4, 0.16666666666666666)]

The 1. is to force float division