如何将矩阵转换为3D数组或反之亦然？

Question

我想将矩阵转换为3D数组，或将3D数组转换为矩阵。如何输入数据以及如何在Python中完成转换工作？

我找了很多地方，但没有答案。请帮我

矩阵：

a b c 
d 1 2 3 
e 2 3 4 
f 4 3 2 

数组b：

a d 1 
a e 2 
a f 4 
b d 2 
b e 3 
b f 3 
c d 3 
c e 4 
c f 2 

我可以用堆栈（）来实现我的目标是什么？

喜欢：Python pandas - pd.melt a dataframe with datetime index results in NaN

Answer 1

所以你的数据不是真正三维的，但2维。你本质上是试图去除你的2d数据。这通常被称为melt。您最好的选择是将数据加载到pandas数据帧中。

import pandas as pd 
df = pd.DataFrame([['d',1,2,3],['e',2,3,4],['f',4,3,2]], columns=['idx','a','b','c']) 

df 
# returns: 
    idx a b c 
0 d 1 2 3 
1 e 2 3 4 
2 f 4 3 2 

pd.melt(df, id_vars='index', value_vars=list('abc')) 
# returns: 
    idx variable value 
0 d  a  1 
1 e  a  2 
2 f  a  4 
3 d  b  2 
4 e  b  3 
5 f  b  3 
6 d  c  3 
7 e  c  4 
8 f  c  2 

Answer 2

我不是很熟悉的大熊猫库，但这里是用Python标准库粗略的解决方案：

#!/usr/bin/env python2 
""" 
Convert a matrix to 2D arrays and vice versa 
http://stackoverflow.com/questions/43289673 
""" 

from collections import OrderedDict 


TEST_MATRIX = """\ 
    a b c 
d 1 2 3 
e 2 3 4 
f 4 3 2 
""" 


def parse_matrix(matrix_string): 
    """Parse a matrix string and return list of tuples representing data""" 
    matrix_string = matrix_string.strip() 
    list_of_lines = matrix_string.splitlines() 
    parsed_list = [] 
    y_headers = list_of_lines[0].split() 
    data_rows = [i.split() for i in list_of_lines[1:]] 
    for y in y_headers: 
     for row in data_rows: 
      parsed_list.append((y, row[0], row[y_headers.index(y) + 1])) 
    return parsed_list 


def convert_to_matrix(data): 
    """ 
    Convert a parsed matrix (in the form of a list of tuples) to a matrix 
    (string) 
    """ 
    # Messes up ordering 
    # y_headers = set(i[0] for i in data) 
    # x_headers = set(i[1] for i in data) 

    y_headers = OrderedDict() 
    x_headers = OrderedDict() 
    [(y_headers.setdefault(i[0]), x_headers.setdefault(i[1])) for i in data] 

    matrix_string = " " + " ".join(y_headers) # header 
    for x in x_headers: 
     row = [x] 
     for y in y_headers: 
      val = [i[-1] for i in data if i[0] == y and i[1] == x][0] 
      row.append(val) 
     row_string = " ".join(row) 
     matrix_string += "\n" + row_string 
    return matrix_string 


def main(): 
    print("Test matrix:") 
    print(TEST_MATRIX) 

    # parse the test matrix string to a list of tuples 
    parsed_test_matrix = parse_matrix(TEST_MATRIX) 
    # print the parsed matrix 
    print("Parsed matrix:") 
    for row in parsed_test_matrix: 
     print " ".join(row) 
    print 

    # convert parsed matrix back to the original matrix and print 
    print("Convert parsed matrix back to matrix:") 
    print(convert_to_matrix(parsed_test_matrix)) 


if __name__ == "__main__": 
    main()