Preparation
Before any data manipulation can occur, two (2) new libraries will require installation.
- The Pandas library enables access to/from a DataFrame.
- The NumPy library supports multi-dimensional arrays and matrices in addition to a collection of mathematical functions.
To install these libraries, navigate to an IDE terminal. At the command prompt ($
), execute the code below. For the terminal used in this example, the command prompt is a dollar sign ($
). Your terminal prompt may be different.
$ pip install pandas
Hit the <Enter>
key on the keyboard to start the installation process.
$ pip install numpy
Hit the <Enter>
key on the keyboard to start the installation process.
If the installations were successful, a message displays in the terminal indicating the same.
Feel free to view the PyCharm installation guide for the required libraries.
Add the following code to the top of each code snippet. This snippet will allow the code in this article to run error-free.
import pandas as pd import numpy as np
DataFrame cumsum()
The cumsum()
method returns a DataFrame/Series of the same size containing the cumulative sum.
The syntax for this method is as follows:
DataFrame.cumsum(axis=None, skipna=True, *args, **kwargs)
Parameters | Description |
---|---|
axis | If zero (0) or index is selected, apply the function to each column. Default is None . If one (1) is selected, apply the function to each row. |
skipna | This parameter excludes NaN or NULL values. If a row/column contains these values, the result is NaN. By default, this is True . |
*args | Additional keywords have no effect. However, they might be compatible with NumPy. |
**kwargs | Additional keywords have no effect. However, they might be compatible with NumPy. |
This example displays the cumulative sum of the Hockey Team Stats.
df_teams = pd.DataFrame({'Bruins': [4, 5, 9], 'Oilers': [3, 6, 10], 'Leafs': [2, 7, 11], 'Flames': [1, 8, 12]}) result = df_teams.cumsum(axis='index') print(result)
- Line [1] creates a DataFrame from a Dictionary of Lists and saves it to
df_teams
. - Line [2] retrieves the cumulative sum and saves them to the
result
variable. - Line [3] outputs the result to the terminal.
Output
Bruins | Oilers | Leafs | Flames | |
0 | 4 | 3 | 2 | 1 |
1 | 9 | 9 | 9 | 9 |
2 | 18 | 19 | 20 | 21 |
π‘ Note: By default, Line [6] iterates over all the rows and determines the value for each column. This is equivalent to axis=None
or axis=βindexβ
(used in our example).
More Pandas DataFrame Methods
Feel free to learn more about the previous and next pandas DataFrame methods (alphabetically) here:
Also, check out the full cheat sheet overview of all Pandas DataFrame methods.