Adventures in Machine Learning

The Power of Groupby Function in Pandas Library and Importance of Datasets

Groupby Function in Pandas Library

The groupby function is an essential tool in the pandas library that allows users to categorize their data into subsets based on specific conditions. This function combines the three main steps of data analysis: splitting, applying, and combining.

Syntax and Arguments

The groupby function syntax looks like this:

DataFrame.groupby(by=None, axis=0, level=None, as_index=True, sort=True, group_keys=True, observed=False, dropna=True)

The arguments used in the syntax are as follows:

  1. by: This is the column or columns to be used to group the data.

    It can be a single column name or a list of column names.

  2. axis: This refers to the axis to be grouped. By default, axis=0, which means it groups the rows, while axis=1 groups the columns.

  3. level: This is used with hierarchical index DataFrame to specify the level of grouping if you have an index with multiple levels.

  4. as_index: This parameter allows you to choose whether the grouped columns should be used as the index of the resulting DataFrame.

  5. sort: When this is set to True, the group keys will be sorted.

    Setting it to False prevents the sorting of group keys.

  6. group_keys: This parameter takes a Boolean value. If True, the keys used for grouping will be included as the first level of the output index.

  7. observed: This argument determines if all values in the grouping column are observed or not.

    If True, only the observed values will be used, and the missing values will be ignored.

  8. dropna: This parameter drops the missing values from the group keys.

Example Using Diabetes Dataset

To better understand how the groupby function works, let’s use an example. Consider a diabetes dataset containing various information about patients.

We can use the groupby function to group the data based on age, insulin, or blood pressure. Groupby by Age:

Grouping the data by age requires the following code:


This returns a groupby object, which we can use to apply various functions like mean, median, min, max, etc.

Groupby by Insulin and BloodPressure:

We can also group the data using multiple columns like insulin and blood pressure. The code would look like this:


This would group the data according to insulin and blood pressure levels, allowing us to calculate the mean or median values.

Groupby by Month

We can also group the data by month, which is a common task when dealing with time series data. There are different ways to achieve this.

Using dt Accessor:

The dt accessor is a powerful tool that allows us to access various datetime properties of a datetime object, including the month property. We can use it to group data by month like this:


Using Resample:

The resample method is another way to group data by month.

It is particularly useful in situations where we want to analyze unique distributions of time series data. The resample method can be used like this:


This approach provides a monthly mean value for their respective column.

Using Grouper:

We can also use the Grouper class to group data by month. The Grouper class allows us to specify the frequency, which is set to ‘M’ for month.

The code for grouping by month using Grouper would look like this:

df.groupby(pd.Grouper(key='Date', freq='M')).mean()


The groupby function is an essential tool for any data analyst or data scientist looking to classify data into subsets based on specific conditions or criteria. The function is versatile and can be used for a wide range of use cases, including time series analysis.

By understanding how to use this function, you gain a deeper understanding of your data and can draw more meaningful insights from it. Datasets play an essential role in data science and machine learning.

They are collections of data that can be used to train, test, and validate models. Datasets are crucial for any data analysis or machine learning project as they provide the fundamental raw material that these fields rely on.

What is a Dataset?

In simple terms, a dataset is a collection of data. It is a structured or unstructured set of data that can be analyzed.

Data is usually collected from various sources, such as surveys, experiments, observations, and from already existing data sources. Datasets can be categorized as small or large, depending on their size.

Importance of Datasets

The importance of datasets cannot be overstated. Datasets are used in various fields such as finance, healthcare, marketing, sports, politics, and education, among others.

In data science and machine learning, datasets are used to train, validate, and test models. Without datasets, data science and machine learning would not be possible.

Types of Datasets

There are several types of datasets. Some of them are listed below.

  1. Structured Dataset – A structured dataset is a type of dataset that can be organized into a specific format or structure, making it easier to analyze.

    This kind of dataset typically contains a table of rows and columns, where each column corresponds to a specific feature, and each row corresponds to an observation or record.

  2. Unstructured Dataset – An unstructured dataset is the opposite of a structured dataset. It contains data that does not fit into a specific structure or format.

    Examples include text, images, audio, and videos which can be analyzed using various machine learning techniques.

  3. Time Series Dataset – This type of dataset contains data that is organized in chronological order. It is commonly used in finance, weather, and social media applications.

  4. Cross-Sectional Dataset – A cross-sectional dataset is a type of dataset that captures data at a single point in time.

    It provides information about a particular population or sample at a specific point in time.

  5. Longitudinal Dataset – This type of dataset captures data over a specific period. It is collected from the same group of people, and thus, it can be used to track changes over time.

  6. Public Dataset – Public datasets are those that are available for free to the public.

    They are usually available on websites such as Kaggle, UCI Machine Learning Repository, and Google Public Datasets.

  7. Private Dataset – A private dataset is a type of dataset that is not available to the public. This type of dataset is usually owned by an organization or individual and may require permission to access.


In conclusion, datasets are essential for any data analysis or machine learning project. They provide the raw material for building and testing machine learning models, and they provide insights that lead to better decision making.

Understanding the different types of datasets, their formats, and structures is crucial in leveraging them effectively. Additionally, paying attention to data ethics, privacy, and security concerns should be a priority when handling datasets, whether public or private.

In summary, datasets are essential collections of structured or unstructured data used in data science and machine learning. They are vital in building and testing machine learning models and deriving insights that lead to better decision making.

There are several types of datasets, including structured, unstructured, time-series, cross-sectional, public, and private datasets. Understanding the types of datasets, their structures, and formats is crucial in leveraging them effectively.

Nevertheless, it is essential to take into account data ethics, privacy, and security when handling datasets. As such, utilizing the right techniques and ethical practices is critical.

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