如何根据df列的唯一值与索引首次出现的位置绘制散点图？

import pandas as pd
import matplotlib.pyplot as plt

# 假设数据已经存在于一个名为df的DataFrame对象中
df = pd.DataFrame(data)

unique_values = df['column_name'].unique()
first_occurrences = df['column_name'].drop_duplicates(keep='first').index

plt.scatter(first_occurrences, unique_values)
plt.xlabel('Index')
plt.ylabel('Unique Values')
plt.title('Scatter Plot of Unique Values vs First Occurrences')
plt.show()