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Data Preprocessing, Analysis, and Visualization for building a Machine learning model

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  • Last Updated : 27 Oct, 2022
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In this article, we are going to see the concept of Data Preprocessing, Analysis, and Visualization for building a Machine learning model. Business owners and organizations use Machine Learning models to predict their Business growth. But before applying machine learning models, the dataset needs to be preprocessed.

So, let’s import the data and start exploring it.

Importing Libraries and Dataset

We will be using these libraries : 

  • Pandas library is used for data analysis.
  • Numpy library is used for complex mathematical operations.
  • Scikit-learn for model training and score evaluation. 


import pandas as pd
import numpy as np
from sklearn.preprocessing import LabelEncoder
from sklearn.preprocessing import OneHotEncoder
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import StandardScaler
dataset = pd.read_csv('Churn_Modelling.csv')

Now let us observe the dataset.



Output :

Top 5 rows of the dataset


Info() function retrieves the information about the dataset such as data type, number of rows and columns, etc.


Output :

Information of the dataset


Exploratory data analysis and visualization

To find out the correlation between the features, Let’s make the heatmap



Output :



Now we can also explore the distribution of CreditScore, Age, Balance, ExtimatedSalary using displot.


lis = ['CreditScore', 'Age', 'Balance', 'EstimatedSalary']
plt.subplots(figsize=(15, 8))
index = 1
for i in lis:
    plt.subplot(2, 2, index)
    index += 1

Output :

Distribution of some features


We can also check the categorical count of each category in Geography and Gender.


lis2 = ['Geography', 'Gender']
plt.subplots(figsize=(10, 5))
index = 1
for col in lis2:
    y = dataset[col].value_counts()
    plt.subplot(1, 2, index)
    sns.barplot(x=list(y.index), y=y)
    index += 1

Output :

Barplot for Categorical Data


Data Preprocessing

Data preprocessing is used to convert raw data into a clear format. Raw data consist of missing values, noisy data, and raw data may be text, image, numeric values, etc.

By the above definition, we understood that transforming unstructured data into a structured form is called data preprocessing. If the unstructured data is used in machine learning models to analyze or to predict, the prediction will be false because unstructured data contains missing values and unwanted data. So for good prediction, the data need to be preprocessed.

Finding Missing Values and Handling them

Let’s observe whether null values are present.



Output :

Checking missing values


Here, True indicates a null value and False indicates there is no null value. We can observe that there are 3 columns containing null values. The 3 columns are Geography, Gender, and Age. Now we need to remove the null values, to do this there are 3 ways they are:

  • Deleting rows
  • Replacing null with custom values
  • Replacing using Mean, Median, and Mode

In this scenario, we replace null values with Mean and Mode.


dataset["Geography"].fillna(dataset["Geography"].mode()[0],inplace = True)
dataset["Gender"].fillna(dataset["Gender"].mode()[0],inplace = True)
dataset["Age"].fillna(dataset["Age"].mean(),inplace = True)

As we know Geography and Gender is a Categorical columns we used mode and Age is an integer type so we used mean.

Note: By using “Inplace = True”, the original data set is modified.

Now once again let us check if any null values still exist.



Checking missing values


Label Encoding

Label Encoding is used to convert textual data to integer data. As we know there are two textual data type columns which are “Geography” and “Gender”. 


le = LabelEncoder()
dataset['Geography'] = le.fit_transform(dataset["Geography"])
dataset['Gender'] = le.fit_transform(dataset["Gender"])

First we initialized LabelEncoder() function, then transformed textual data to integer data with fit_transform() function.

So now, the “Geography” and “Gender” columns are converted to integer data types.

Splitting Dependent and Independent Variables

Dataset is split into x and y variables and converted to an array. 


x = dataset.iloc[:,3:13].values
y = dataset.iloc[:,13:14].values

Here x is the independent variable and y is the dependent variable.

Splitting into Train and Test Dataset 


x_train, x_test, y_train, y_test = train_test_split(x,y,
                                                    test_size = 0.2
                                                    random_state = 0)

Here we split data into train and test sets.

Feature Scaling

Feature Scaling is a technique done to normalize the independent variables.


sc = StandardScaler()
x_train = sc.fit_transform(x_train)
x_test = sc.fit_transform(x_test)

We have successfully preprocessed the dataset. And now we are ready to apply Machine Learning models.

Model Training and Evaluation

As this is a Classification problem then we will be using the below models for training the data.

And for evaluation, we will be using Accuracy Score.


from sklearn.neighbors import KNeighborsClassifier
from sklearn.ensemble import RandomForestClassifier
from sklearn.svm import SVC
from sklearn.linear_model import LogisticRegression
from sklearn import metrics
knn = KNeighborsClassifier(n_neighbors=3)
rfc = RandomForestClassifier(n_estimators = 7,
                             criterion = 'entropy',
                             random_state =7)
svc = SVC()
lc = LogisticRegression()
# making predictions on the training set
for clf in (rfc, knn, svc,lc):, y_train)
    y_pred = clf.predict(x_test)
    print("Accuracy score of ",clf.__class__.__name__,"=",
          100*metrics.accuracy_score(y_test, y_pred))

Output : 

Accuracy score of  RandomForestClassifier = 84.5
Accuracy score of  KNeighborsClassifier = 82.5
Accuracy score of  SVC = 86.15
Accuracy score of  LogisticRegression = 80.75


Random Forest classifier and SVC are showing the best results with an accuracy of around 85%

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