Book Image

Applied Supervised Learning with Python

By : Benjamin Johnston, Ishita Mathur
Book Image

Applied Supervised Learning with Python

By: Benjamin Johnston, Ishita Mathur

Overview of this book

Machine learning—the ability of a machine to give right answers based on input data—has revolutionized the way we do business. Applied Supervised Learning with Python provides a rich understanding of how you can apply machine learning techniques in your data science projects using Python. You'll explore Jupyter Notebooks, the technology used commonly in academic and commercial circles with in-line code running support. With the help of fun examples, you'll gain experience working on the Python machine learning toolkit—from performing basic data cleaning and processing to working with a range of regression and classification algorithms. Once you’ve grasped the basics, you'll learn how to build and train your own models using advanced techniques such as decision trees, ensemble modeling, validation, and error metrics. You'll also learn data visualization techniques using powerful Python libraries such as Matplotlib and Seaborn. This book also covers ensemble modeling and random forest classifiers along with other methods for combining results from multiple models, and concludes by delving into cross-validation to test your algorithm and check how well the model works on unseen data. By the end of this book, you'll be equipped to not only work with machine learning algorithms, but also be able to create some of your own!
Table of Contents (9 chapters)

Chapter 1: Python Machine Learning Toolkit

Activity 1: pandas Functions


  1. Open a new Jupyter notebook.

  2. Use pandas to load the Titanic dataset:

    import pandas as pd
    df = pd.read_csv('titanic.csv')

    Use the head() function on the dataset as follows:

    # Have a look at the first 5 sample of the data

    The output will be as follows:

    Figure 1.65: First five rows

    Use the describe function as follows:


    The output will be as follows:

    Figure 1.66: Output of describe()

  3. We don't need the Unnamed: 0 column. We can remove the column without using the del command, as follows:

    df = df[df.columns[1:]] # Use the columns

    The output will be as follows:

    Figure 1.67: First five rows after deleting the Unnamed: 0 column

  4. Compute the mean, standard deviation, minimum, and maximum values for the columns of the DataFrame without using describe:

    Fare        33.295479
    Pclass       2.294882
    Age         29.881138
    Parch        0.385027
    SibSp        0.498854
    Survived     0.383838
    dtype: float64
    Fare        51.758668
    Pclass       0.837836
    Age         14.413493
    Parch        0.865560
    SibSp        1.041658
    Survived     0.486592
    dtype: float64
    Fare        0.00
    Pclass      1.00
    Age         0.17
    Parch       0.00
    SibSp       0.00
    Survived    0.00
    dtype: float64
    Fare        512.3292
    Pclass        3.0000
    Age          80.0000
    Parch         9.0000
    SibSp         8.0000
    Survived      1.0000
    dtype: float64
  5. What about the 33, 66, and 99% quartiles? Use the quantile method as follows:

    Fare         8.559325
    Pclass       2.000000
    Age         23.000000
    Parch        0.000000
    SibSp        0.000000
    Survived     0.000000
    Name: 0.33, dtype: float64
    Fare        26.0
    Pclass       3.0
    Age         34.0
    Parch        0.0
    SibSp        0.0
    Survived     1.0
    Name: 0.66, dtype: float64
    Fare        262.375
    Pclass        3.000
    Age          65.000
    Parch         4.000
    SibSp         5.000
    Survived      1.000
    Name: 0.99, dtype: float64
  6. How many passengers were from each class? Let's see, using the groupby method:

    class_groups = df.groupby('Pclass')
    for name, index in class_groups:
        print(f'Class: {name}: {len(index)}')
    Class: 1: 323
    Class: 2: 277
    Class: 3: 709
  7. How many passengers were from each class? You can find the answer by using selecting/indexing methods to count the members of each class:

    for clsGrp in df.Pclass.unique():
        num_class = len(df[df.Pclass == clsGrp])
        print(f'Class {clsGrp}: {num_class}')
    Class 3: 709
    Class 1: 323
    Class 2: 277

    The answers to Step 6 and Step 7 do match.

  8. Determine who the eldest passenger in third class was:

    third_class = df.loc[(df.Pclass == 3)]
    third_class.loc[(third_class.Age == third_class.Age.max())]

    The output will be as follows:

    Figure 1.68: Eldest passenger in third class

  9. For a number of machine learning problems, it is very common to scale the numerical values between 0 and 1. Use the agg method with Lambda functions to scale the Fare and Age columns between 0 and 1:

    fare_max = df.Fare.max()
    age_max = df.Age.max()
        'Fare': lambda x: x / fare_max, 
        'Age': lambda x: x / age_max,

    The output will be as follows:

    Figure 1.69: Scaling numerical values between 0 and 1

  10. There is one individual in the dataset without a listed Fare value:

    df_nan_fare = df.loc[(df.Fare.isna())]

    This is the output:

    Figure 1.70: Individual without a listed Fare value

    Replace the NaN values of this row in the main DataFrame with the mean Fare value for those corresponding with the same class and Embarked location using the groupby method:

    embarked_class_groups = df.groupby(['Embarked', 'Pclass'])
    indices = embarked_class_groups.groups[(df_nan_fare.Embarked.values[0], df_nan_fare.Pclass.values[0])]
    mean_fare = df.iloc[indices].Fare.mean()
    df.loc[(df.index == 1043), 'Fare'] = mean_fare

    The output will be as follows:

    Cabin                      NaN
    Embarked                     S
    Fare                   14.4354
    Pclass                       3
    Ticket                    3701
    Age                       60.5
    Name        Storey, Mr. Thomas
    Parch                        0
    Sex                       male
    SibSp                        0
    Survived                   NaN
    Name: 1043, dtype: object