合并使我在数据框中有更多行

Question

更新：如评论中所述，我的索引不是唯一的。通过pivot.table解决了

我得到了以下代码来在df上执行聚类。此df大约为80 K行（df称为“ Kmeans”）。然后，我有另一个与'Kmeans'（即'SKU_NR'）具有共同值的df，其行数略少于80K（此df被命名为'Historie'）。我想将df'Kmeans'与df'Historie'合并，但是当我这样做时，它给了我2百万行。我以前做过，然后成功了。代码出了什么问题？

#load in libraries
import pandas as pd
import numpy as np
pd.options.mode.chained_assignment = None
import warnings
warnings.simplefilter(action='ignore', category=FutureWarning)

 #Load and prepare data
 Historie = pd.read_excel("file.xlsx")

 Kmeans = Historie[['SKU_NR','ORDER_ADV_CONS_UNITS_WK_PICK']]

 Kmeans = Kmeans.dropna()

 from sklearn.cluster import KMeans
 km = KMeans(n_clusters=3)
 km.fit(Kmeans)
 km.predict(Kmeans)
 labels = km.labels_
 Kmeans["Classification"] = labels
 Kmeans = Kmeans[["SKU_NR","Classification"]]

 Historie 
 =Historie[['SKU_NR','WEEKNR','ORDER_ADV_CONS_UNITS_WK_PICK',
 'FORECAST_NEC_STOCK_BASE']]
 Historie = Historie.merge(Kmeans, on = "SKU_NR")