Adventures in Machine Learning

4 Advanced Pandas Techniques for Data Analysis

Using GroupBy with Bin Counts in Pandas

Have you ever needed to know the frequency of a specific variable broken down by a different variable? In data analysis, this task is quite common.

Luckily, by using the groupby function in the pandas library, this task can be accomplished with ease. In this article, we will explore the syntax for calculating bin counts of one variable grouped by another variable, and we will use basketball data to demonstrate how to calculate the frequency of points for each team.

Syntax for Calculating Bin Counts in Pandas

The groupby function is a powerful tool in pandas that allows the user to group data by a certain variable. With the addition of the value_counts and hist functions, we can calculate the frequency of a certain variable and create a histogram to visualize the distribution.

To calculate the bin counts of one variable grouped by another variable, we use this syntax:

“`python

df.groupby(‘variable1’)[‘variable2’].value_counts()

“`

Here, variable1 is the variable you want to group by, and variable2 is the variable you want to calculate the frequency of. This syntax groups the data by variable1, takes all unique values of variable2, and counts the frequency of each unique value of variable2 for every group of variable1.

Example of Using the Syntax to Calculate the Frequency of Points for Each Basketball Team

Let’s suppose we have a dataset of basketball games that includes the name of each team and the number of points they scored. | Team | Points |

|——|——–|

| A | 87 |

| A | 91 |

| B | 78 |

| B | 82 |

| B | 79 |

| C | 90 |

| C | 87 |

| C | 79 |

| D | 71 |

| D | 80 |

| D | 85 |

| D | 82 |

To calculate the frequency of points for each team, we’ll use the above syntax:

“`python

df.groupby(‘Team’)[‘Points’].value_counts()

“`

This produces the following output:

| Team | Points | Frequency |

|——|——–|———–|

| A | 87 | 1 |

| A | 91 | 1 |

| B | 78 | 1 |

| B | 79 | 1 |

| B | 82 | 1 |

| C | 79 | 1 |

| C | 87 | 1 |

| C | 90 | 1 |

| D | 71 | 1 |

| D | 80 | 1 |

| D | 82 | 1 |

| D | 85 | 1 |

Now we can see how many times each team scored each number of points.

For example, team A scored 87 points once and scored 91 points once.

Defining Bins

In many cases, it’s useful to group a continuous variable into discrete bins. A good example is when working with age data; instead of looking at ages individually, we can group them into ranges like 20-29, 30-39, etc.

Pandas provides a simple and convenient way to define bins using the pd.cut() function. Using pd.cut() Function to Define Bins

The pd.cut() function allows the user to define the ranges of each bin, and it will automatically group the data into those bins.

Here’s the syntax for the pd.cut() function:

“`python

pd.cut(x, bins, right=True, labels=None, retbins=False, precision=3, include_lowest=False, duplicates=’raise’)

“`

Here, x is the data that needs to be binned, and bins is the specified range of each bin. For example, the following code groups the points in the basketball dataset into bins of 10:

“`python

bins = [70, 80, 90, 100]

pd.cut(df[‘Points’], bins)

“`

This produces the following output:

| | Points |

|——-|——–|

| (80,90]| 87 |

| (80,90]| 91 |

| (70,80]| 78 |

| (80,90]| 82 |

| (70,80]| 79 |

| (80,90]| 90 |

| (80,90]| 87 |

| (70,80]| 79 |

| (70,80]| 71 |

| (70,80]| 80 |

| (80,90]| 82 |

| (80,90]| 85 |

As you can see, the points have now been grouped into three bins: (70,80], (80,90], and (90,100].

The data in each row represents a point total that falls within one of these bins.

Example of Defining Different Bins for Point Ranges

To illustrate how binning works, let’s say we want to create six different bins for the point ranges. The following code demonstrates how to define the bin ranges and group the data into them:

“`python

bins = [0, 60, 70, 80, 90, 100, 110]

labels = [‘below 60′, ’60-70′, ’70-80′, ’80-90′, ’90-100’, ‘above 100’]

df[‘PointRange’] = pd.cut(df[‘Points’], bins=bins, labels=labels)

df.groupby(‘Team’)[‘PointRange’].value_counts()

“`

This produces the following output:

| Team | PointRange | Frequency |

|——|————|———–|

| A | 90-100 | 1 |

| A | 80-90 | 1 |

| B | 70-80 | 1 |

| B | 80-90 | 2 |

| C | 80-90 | 1 |

| C | 90-100 | 1 |

| C | 70-80 | 1 |

| D | below 60 | 0 |

| D | 70-80 | 1 |

| D | 80-90 | 2 |

| D | 90-100 | 0 |

| D | above 100 | 0 |

We can now see how many times each team’s point total falls into each of the six bins.

For instance, team B scored between 80-90 points twice, whereas team D didn’t score in the below-60 or above-100 bins.

Conclusion

In conclusion, groupby with bin counts and binning are essential techniques in data analysis. This article showed you how to use pandas to calculate bin counts of one variable grouped by another variable and how to define bins with the pd.cut() function.

We used basketball data to illustrate how to calculate the frequency of points for each team and demonstrated how to define different point range bins. We hope this article was helpful and allowed you to better understand these critical data analysis concepts.

Applying GroupBy to Categorical Variables

GroupBy functionality in pandas is not limited to numerical data typesit can also be applied to categorical variables, such as strings or even boolean values. By using the groupby function and specifying the categorical variable as the parameter, we can aggregate data and perform operations on categorical variables, just like with numerical variables.

Syntax for

Applying GroupBy to Categorical Variables

To apply the groupby function to categorical variables, we use the same syntax as we would with numerical variables. Here’s an example:

“`python

df.groupby(‘categorical_variable’)[‘numerical_variable’].agg(‘operation’)

“`

In this syntax, categorical_variable is the categorical variable we want to group the data by, and numerical_variable is the numerical variable we want to apply the operation to.

operation refers to any one of the aggregation functions, such as sum, mean, or count. Example of

Applying GroupBy to Categorical Variables in a pandas DataFrame

Let’s suppose we have a pandas DataFrame with sales data for different stores, including the store name and the total amount of sales:

| Store Name | Sales |

|————|——-|

| Store A | 2000 |

| Store B | 1500 |

| Store A | 3000 |

| Store C | 2500 |

| Store B | 3500 |

| Store D | 4500 |

| Store C | 2000 |

If we want to group this data by store name and calculate the total sales for each store, we would use the following code:

“`python

df.groupby(‘Store Name’)[‘Sales’].sum()

“`

This produces the following output:

| Store Name | Sales |

|————|——-|

| Store A | 5000 |

| Store B | 5000 |

| Store C | 4500 |

| Store D | 4500 |

As you can see, we have grouped all the data by store name and calculated the total sales for each store.

Custom Aggregation Functions

While pandas offers a variety of built-in aggregation functions, such as sum, mean, and count, sometimes we need to use our custom functions to perform specific operations on our data. Pandas allows us to define and apply custom aggregation functions to our data.

Syntax for Defining and Applying

Custom Aggregation Functions in Pandas

To define a custom aggregation function, we use the def keyword, followed by the function name, and the parameters that we want to include in our function. Here’s an example:

“`python

def my_function(data):

# perform some operation

return result

df.groupby(‘categorical_variable’)[‘numeric_variable’].agg(my_function)

“`

In this syntax, my_function is the name of the custom aggregation function we’re defining.

Within this function, we can include any operations we need to perform on our data. data is the parameter that represents the data we want to apply the operation to, and result is the value we want to return from our function.

Once we’ve defined our custom aggregation function, we can apply it to our data by using the groupby function, as shown in the example above.

Example of Defining and Applying a Custom Aggregation Function to Calculate the Range of Values Within Each Bin

Let’s say we have a dataset of employees and their salaries, and we want to group this data into categories based on salary range. Instead of using one of the built-in aggregation functions, we want to define a custom function that calculates the range of salaries within each bin.

Here’s the code to define and apply our custom function:

“`python

def salary_range(data):

return max(data) – min(data)

bins = [0, 25000, 50000, 75000, 100000]

labels = [‘A’, ‘B’, ‘C’, ‘D’]

df[‘Salary Range’] = pd.cut(df[‘Salary’], bins=bins, labels=labels)

df.groupby(‘Salary Range’)[‘Salary’].agg(salary_range)

“`

In this code, we define our custom function salary_range that takes in the data we want to apply our function to, calculates the range of salaries within that group, and returns the result. We then define our salary bins and apply the pd.cut() function to our data, creating a new column called Salary Range.

We then use the groupby function to group the data by salary range and apply the custom function to calculate the range of salaries for each group. The output of this code will show the range of salaries for each salary bin:

| Salary Range | Salary |

|————–|——–|

| A | 16000 |

| B | 47000 |

| C | 60000 |

| D | 90000 |

As you can see, we’ve successfully defined and applied a custom aggregation function to our data, allowing us to perform a specific operation on our grouped data.

Conclusion

In this addition to the article, we explored how to apply GroupBy to categorical variables and how to define and apply custom aggregation functions in pandas. By using these advanced pandas tools, we can perform specific operations on our data and gain deeper insights that might not be possible with built-in aggregation functions alone.

We encourage you to explore these concepts further to improve your data analysis skills.

MultiIndex GroupBy

In pandas, we can use the GroupBy function to analyze data by a single variable. However, what if we want to group our data by multiple variables?

The solution is to use

MultiIndex GroupBy. This tool allows us to group data by more than one variable and perform more complex analysis. Syntax for Using

MultiIndex GroupBy in Pandas

To use

MultiIndex GroupBy in pandas, we can use the groupby function by passing a list of the variables we want to group by.

For example, if we have a DataFrame of sales data that includes the store name, city, and the total amount of sales, we can group the data by both store name and city using the following syntax:

“`python

df.groupby([‘store’, ‘city’])[‘sales’].sum()

“`

In this syntax, [store, city] is the list of variables we want to group by, and [sales] is the column we want to apply the operation to. Here, we’re calculating the total sales for each store in each city.

Example of Using

MultiIndex GroupBy to Group Data by More Than One Variable

Let’s create a sample DataFrame to illustrate how

MultiIndex GroupBy works:

“`python

data = {‘city’: [‘Seattle’, ‘Seattle’, ‘Portland’, ‘Portland’, ‘Boise’, ‘Boise’],

‘store’: [‘A’, ‘B’, ‘C’, ‘D’, ‘E’, ‘F’],

‘sales’: [2000, 1500, 3000, 2500, 3500, 4000]}

df = pd.DataFrame(data)

“`

This DataFrame includes the city, store, and sales data. If we want to group the data by both city and store, and calculate the total sales for each group, we can use the following code:

“`python

df.groupby([‘city’, ‘store’])[‘sales’].sum()

“`

This produces the following output:

|city |store |sales |

|———|——-|——|

|Boise |E | 3500 |

| |F | 4000 |

|Portland |C | 3000 |

| |D | 2500 |

|Seattle |A | 2000 |

| |B | 1500 |

As you can see, the data has been grouped first by city and then by store, and the sum of sales has been calculated for each group.

We can also use

MultiIndex GroupBy with more than two variables. For example, if we have a DataFrame that includes sales data for each week for each store and want to group it by city, store, and week, we would use the following code:

“`python

df.groupby([‘city’, ‘store’, ‘week’])[‘sales’].sum()

“`

This allows us to drill down into the data and analyze it at a more granular level.

Conclusion

MultiIndex GroupBy is an advanced tool in pandas that allows us to group data by more than one variable, which can help us perform more complex data analysis. By using the groupby function with a list of variables, we can group our data by multiple variables and apply aggregation functions to perform more complex analysis.

This tool can be particularly helpful when working with large datasets that require more granular analysis. We hope this addition has provided you with a better understanding of

MultiIndex GroupBy and its capabilities in pandas.

In this article, we explored four advanced techniques in pandas that can help data analysts extract more insights from their data. We started by discussing how to calculate bin counts of one variable grouped by another variable using GroupBy, then moved on to defining bins with the pd.cut() function.

We then explored how to apply GroupBy to categorical variables and how to define and apply custom aggregation functions. Finally, we learned how

MultiIndex GroupBy can help

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