Marrciovr - 1 year ago 73

Python Question

I have a pandas DataFrame with some independent columns, and I'm looking for an efficient way to unwind / aggregate them.

So, let's say I have the table:

`+-----+-----+-------+------+-------+`

| One | Two | Three | Four | Count |

+-----+-----+-------+------+-------+

| a | x | y | y | 3 |

+-----+-----+-------+------+-------+

| b | z | x | x | 5 |

+-----+-----+-------+------+-------+

| c | y | x | y | 1 |

+-----+-----+-------+------+-------+

Where rows Two, Three and Four are independent.

I would like to end up with the table:

`+-----+-------+-------+`

| One | Other | Count |

+-----+-------+-------+

| a | x | 3 |

+-----+-------+-------+

| a | y | 6 |

+-----+-------+-------+

| b | x | 10 |

+-----+-------+-------+

| b | z | 5 |

+-----+-------+-------+

| c | x | 1 |

+-----+-------+-------+

| c | y | 2 |

+-----+-------+-------+

How would be the best way to achieve this?

Answer Source

You can use `melt`

function from `pandas`

to reshape your data frame from wide to long format then groupby the `One`

and `Other`

columns and `sum`

the `Count`

column:

```
import pandas as pd
pd.melt(df, id_vars = ['One', 'Count'], value_name = 'Other').groupby(['One', 'Other'])['Count'].sum().reset_index()
One Other Count
0 a x 3
1 a y 6
2 b x 10
3 b z 5
4 c x 1
5 c y 2
```