Determine reverse order of data given X/Y coordinates

user_10964035 0
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Imagine an electrical connector. It has pins. Each pin has a corresponding X/Y location in space. I am trying to figure out how to mirror, or 'flip' each pin on the connector given their X/Y coordinate. note: I am using pandas version 23.4 Rough Paint Sketch Visual We can assume that x,y, and pin are not unique but connector is. Connectors can be any size, so two rows of 5, 3 rows of 6, etc.

x    y    pin   connector
1    1     A       1
2    1     B       1
3    1     C       1
1    2     D       1
2    2     E       1
3    2     F       1  
1    1     A       2
2    1     B       2
3    1     C       2
1    2     D       2
2    2     E       2
3    2     F       2

The dataframe column, 'flip', is the solution I am trying to get to. Notice the pins that would be in the same row are now in reverse order.

x    y    pin    flip   connector
1    1     A       C        1
2    1     B       B        1
3    1     C       A        1
1    2     D       F        1
2    2     E       E        1
3    2     F       D        1  
1    1     A       C        2
2    1     B       B        2
3    1     C       A        2
1    2     D       F        2
2    2     E       E        2
3    2     F       D        2
pandas python
3 Answers

IIUC try using [::-1] a reversing element and groupby with transform:

df['flip'] = df.groupby(['connector','y'])['pin'].transform(lambda x: x[::-1])

Output:

    x  y pin  connector flip
0   1  1   A          1    C
1   2  1   B          1    B
2   3  1   C          1    A
3   1  2   D          1    F
4   2  2   E          1    E
5   3  2   F          1    D
6   1  1   A          2    C
7   2  1   B          2    B
8   3  1   C          2    A
9   1  2   D          2    F
10  2  2   E          2    E
11  3  2   F          2    D
user_63615310 
import io
import pandas as pd

data = """
x    y    pin   connector
1    1     A       1
2    1     B       1
3    1     C       1
1    2     D       1
2    2     E       1
3    2     F       1
1    1     A       2
2    1     B       2
3    1     C       2
1    2     D       2
2    2     E       2
3    2     F       2
"""

#strip blank lines at the beginning and end
data = data.strip()

#make it quack like a file
data_file = io.StringIO(data)

#read data from a "wsv" file (whitespace separated values)
df = pd.read_csv(data_file, sep='\s+')

Make the new column:

flipped = []

for name, group in df.groupby(['connector','y']):
    flipped.extend(group.loc[::-1,'pin'])

df = df.assign(flip=flipped)

df

Final DataFrame:

    x   y   pin     connector   flip
0   1   1   A       1           C
1   2   1   B       1           B
2   3   1   C       1           A
3   1   2   D       1           F
4   2   2   E       1           E
5   3   2   F       1           D
6   1   1   A       2           C
7   2   1   B       2           B
8   3   1   C       2           A
9   1   2   D       2           F
10  2   2   E       2           E
11  3   2   F       2           D
user_58288830

You can create a map between the original coordinates and the coordinates of the 'flipped' component. Then you can select the flipped values.

import numpy as np

midpoint = 2

coordinates_of_flipped = pd.MultiIndex.from_arrays([df['x'].map(lambda x: x - midpoint  * np.sign(x - midpoint )), df['y'], df['connector']])

df['flipped'] = df.set_index(['x', 'y', 'connector']).loc[coordinates_of_flipped].reset_index()['pin']

which gives

Out[30]: 
    x  y pin  connector flipped
0   1  1   A          1       C
1   2  1   B          1       B
2   3  1   C          1       A
3   1  2   D          1       F
4   2  2   E          1       E
5   3  2   F          1       D
6   1  1   A          2       C
7   2  1   B          2       B
8   3  1   C          2       A
9   1  2   D          2       F
10  2  2   E          2       E
11  3  2   F          2       D
user_61086610
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