ค่าใช้จ่ายเฉลี่ยของขั้นตอนที่แพทย์ John Wen ได้รับการฝึกอบรมคือเท่าใด?
What is the average cost of procedures that physician John Wen was trained in?
df_trained_in = pd.DataFrame(columns=['physician', 'treatment']); df_procedures = pd.DataFrame(columns=['cost', 'code']); df_physician = pd.DataFrame(columns=['employeeid', 'name'])
df_procedures[df_procedures['code'].isin(df_trained_in[df_trained_in['physician']==df_physician[df_physician['name']=='John Wen']['employeeid'].values[0]]['treatment'])]['cost'].mean()