Convert a distance matrix to a list of pairwise distances in Python [closed]

Question

Assume the following distance matrix in python...

  0 1 2 3
0 0 1 4 8
1 1 0 3 7
2 4 3 0 3
3 8 7 3 0

I would like to convert this distance matrix to a list of pairwise euclidean distances, as below...

  Obj1  Obj2  Dist
0  0      1    1
1  0      2    4
2  0      3    8
3  1      2    3
4  1      3    7
5  2      3    3

I cannot seem to find any solution to this, but I am new to python so perhaps I just don't know what to search for. Any help would be much appreciated.

Hydrogenous

I'd check out the NumPy and SciPy python libraries: jbencook.com/pairwise-distance-in-numpy. If you provide more details about your problem, I could possibly be of more help. – Bassett

Welcome to SO. This isn't a discussion forum or tutorial. Please take the tour and take the time to read How to Ask and the other links found on that page. Invest some time with the Tutorial practicing the examples. It will give you an idea of the tools Python offers to help you solve your problem. – Isolate

Answer 1

distances = [
    [0, 1, 4, 8],
    [1 ,0, 3, 7],
    [4, 3, 0, 3],
    [8, 7, 3, 0],
]

MATRIX_SIZE = len(distances)
distance_pairs = []
for i in range(MATRIX_SIZE):
    for j in range(i):
        distance_pairs.append(("distance from {} to {} is {}".format(i, j, distances[i][j])))
print(distance_pairs)

Unreasoning

marke, this did exactly what I was looking for! Thank you for the help. My apologies if my question was improperly formatted or structure, I'll take a closer look at the tutorial. – Hydrogenous

Answer 2

You can use Pandas and DataFrame.stack()

import pandas as pd
import io

txt_dist_mat = '''  0 1 2 3
0 0 1 4 8
1 1 0 3 7
2 4 3 0 3
3 8 7 3 0'''

df = pd.read_fwf(io.StringIO(txt_dist_mat), index_col=0)

euc_mat = df.stack().reset_index().rename(columns={'level_0': 'Obj1', 'level_1': 'Obj2', 0: 'Dist'})

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