title: How to show kdeplot in a 5*4 subplot?
body: <p>I am working on a machine learning project and am using the seaborn kdeplot to show the standard scaler after scaling. However, no matter how large the figure size I change, the graphs just can't show and will show the error: <strong>AttributeError: 'numpy.ndarray' object has no attribute 'plot'</strong>.The image I'm willing to show is a 5*4 subplot that look like this:
  <a href="https://i.stack.imgur.com/TRvVJ.png" rel="nofollow noreferrer">expected subplot image</a></p>
  
  <pre><code>#feature scaling
  #since numerical attributes have very different scales, 
  #we use standardization to get all attributes to have the same scale
  import pandas as pd
  import numpy as np
  from sklearn import preprocessing
  import matplotlib
  import matplotlib.pyplot as plt
  import seaborn as sns
  %matplotlib inline
  matplotlib.style.use('ggplot')
  scaler = preprocessing.StandardScaler()
  scaled_df = scaler.fit_transform(train_set)
  scaled_df = pd.DataFrame(scaled_df, columns=["SaleAmount","SaleCount","ReturnAmount","ReturnCount",
                       "KeyedAmount","KeyedCount","VoidRejectAmount","VoidRejectCount","RetrievalAmount",
                           "RetrievalCount","ChargebackAmount","ChargebackCount","DepositAmount","DepositCount",
                    "NetDeposit","AuthorizationAmount","AuthorizationCount","DeclinedAuthorizationAmount","DeclinedAuthorizationCount"])
  fig, axes = plt.subplots(figsize=(20,10), ncols=5, nrows=4)
  sns.kdeplot(scaled_df['SaleAmount'], ax=axes[0])
  sns.kdeplot(scaled_df['SaleCount'], ax=axes[1])
  sns.kdeplot(scaled_df['ReturnAmount'], ax=axes[2])
  sns.kdeplot(scaled_df['ReturnCount'], ax=axes[3])
  sns.kdeplot(scaled_df['KeyedAmount'], ax=axes[4])
  sns.kdeplot(scaled_df['KeyedCount'], ax=axes[5])
  sns.kdeplot(scaled_df['VoidRejectAmount'], ax=axes[6])
  sns.kdeplot(scaled_df['VoidRejectCount'], ax=axes[7])
  sns.kdeplot(scaled_df['RetrievalAmount'], ax=axes[8])
  sns.kdeplot(scaled_df['RetrievalCount'], ax=axes[9])
  sns.kdeplot(scaled_df['ChargebackAmount'], ax=axes[10])
  sns.kdeplot(scaled_df['ChargebackCount'], ax=axes[11])
  sns.kdeplot(scaled_df['DepositAmount'], ax=axes[12])
  sns.kdeplot(scaled_df['DepositCount'], ax=axes[13])
  sns.kdeplot(scaled_df['NetDeposit'], ax=axes[14])
  sns.kdeplot(scaled_df['AuthorizationAmount'], ax=axes[15])
  sns.kdeplot(scaled_df['AuthorizationCount'], ax=axes[16])
  sns.kdeplot(scaled_df['DeclinedAuthorizationAmount'], ax=axes[17])
  sns.kdeplot(scaled_df['DeclinedAuthorizationCount'], ax=axes[18])
  </code></pre>