Numpy - 从数组创建摘要 df

Question

I have a 2d array of 20,10, values ranging from 0 to 12 (created from a dataframe).

arr = np.random.choice(np.arange(0, 13), size=(20,10))
array([[0,  9,  9,  7,  6,  2,  6,  4,  4,  3],
       [0,  2,  1,  7,  1,  0,  2,  6,  6,  2],
       [7,  3,  9,  8,  9,  7,  1, 10,  4,  2],
       [0,  7,  0,  1,  4,  5,  8,  4,  2,  2],
       [5,  2, 12,  3, 12,  2,  7, 12,  4, 12],
       [0, 11,  0, 10,  7,  4, 12, 11, 11,  4],
       [0,  9,  9,  8,  5, 11,  7,  6, 10,  7],
       [0,  9,  0, 10, 11,  1,  5, 10,  8, 10],
       [3, 11,  4,  7,  7,  8, 10, 11,  5, 12],
       [0,  5,  0,  8,  1,  5,  1, 11,  9,  1],
       [0,  8,  6, 12, 11,  1,  4, 11,  4,  1],
       [2, 10,  5,  5,  7,  9, 11,  6, 12, 10],
       [9,  8, 11,  4, 10,  1, 10, 12,  0,  3],
       [0,  7, 10,  8,  2, 10,  5,  7,  9,  6],
       [0,  9,  6,  9,  1, 12,  4,  1,  8,  2],
       [8, 12, 10, 12,  8,  2,  3,  0, 11,  4],
       [6,  7, 11, 12,  8,  7,  1,  9,  9,  8],
       [0,  4,  0,  8,  9,  7,  1,  1,  3,  5],
       [0,  8,  1, 11,  2, 12,  6, 11, 12, 10],
       [0,  7,  3,  8,  3,  3,  7,  1,  9,  9]])

Desired output is a dataframe with rows and columns going from 0 to 12. And the cell values should be the count of number of consecutive times a value changes from one value to another in all rows of the array.

    0   1   2   3   4   5   6   7   8   9   10  11  12
0   25  20  30                                      
1                                                   
2                                                   
3                                                   
4   2   2   5           4                           
5                                                   
6                                                   
7                                                   
8                                                   
9                                                   
10                                                  
11                                                  
12                                                  

(Not true output)

For example, in this array, 0 to 9 change occurs 4 times. And 10 to 12 change occurs 2 times:

Answer 1

If you use a Counter from collections library you can solve it like this

import numpy as np
from collections import Counter

max_number = 12

np.random.choice(np.arange(0, max_number+1), size=(20,10))

index = np.array(list((i, i+1) for i in range(array.size-1)))

counter = Counter(map(tuple, tuple(array.reshape(-1)[index].tolist())))

result = np.zeros(shape=(max_number,max_number))

for i in range(max_number):
    for j in range(max_number):
        result[i,j] = counter[(i,j)]

result

Answer 2

This is my solution. Can it be improved?

max_ = arr.max()

shape_ = np.arange(arr.min(), arr.max() + 1)
df = pd.DataFrame(index=shape_, columns=shape_)
df.fillna(0, inplace=True)

for row in arr:
    for i in range(len(row) - 1):
        df[row[i]][row[i + 1]] += 1

df.T
>>
    0   1   2   3   4   5   6   7   8   9   10  11  12
0   0   1   2   1   1   1   0   3   4   4   2   2   0
1   1   1   0   1   2   2   0   1   1   2   2   2   1
2   0   1   1   1   0   0   2   1   0   0   2   0   2
3   1   0   0   1   0   1   0   1   1   1   0   1   1
4   1   2   2   1   1   1   0   1   0   0   1   1   2
5   1   1   1   0   0   1   0   2   1   0   1   1   1
6   0   0   2   0   1   0   1   1   0   1   1   1   2
7   1   5   0   2   1   0   2   1   1   2   1   1   1
8   0   2   3   1   1   1   1   1   0   2   2   1   1
9   1   2   0   0   0   0   2   3   4   4   0   1   0
10  0   1   0   0   1   2   0   2   2   0   0   2   2
11  1   2   1   0   5   1   1   1   0   1   0   1   2
12  1   0   1   1   2   0   1   0   2   0   3   2   0