对列中值相等的行求和

Question

如何在numpy数组的第一列中具有相等值的行之间求和？例如:

In: np.array([[1,2,3],
             [1,4,6], 
             [2,3,5],
             [2,6,2],
             [3,4,8]])

Out: [[1,6,9], [2,9,7], [3,4,8]]

任何帮助将不胜感激.

Answer 1

Pandas有一个非常强大的groupby功能,这使得这非常简单.

import pandas as pd

n = np.array([[1,2,3],
             [1,4,6], 
             [2,3,5],
             [2,6,2],
             [3,4,8]])

df = pd.DataFrame(n, columns = ["First Col", "Second Col", "Third Col"])

df.groupby("First Col").sum()