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Pandas Backward Fill from Another Column

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by Abdul Rawoof A R dot icon Updated: Jan 31, 2023

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Backward fill from another column refers to a process where missing values in one column of a Pandas DataFrame are filled with the values from the previous row of another column. This is done using the .bfill() method, which stands for "backward fill." 


There are several potential applications for using the .bfill() method to backward fill missing values in a column of a Pandas DataFrame from the values of another column. Some examples include: 

  • Data cleaning and pre-processing: Backward fill can ensure that the data is complete and ready for further analysis. 
  • Time series analysis: In time series data, the backward fill can ensure that the data is consistent and complete over a given period. 
  • Financial analysis: In financial data, the backward fill can ensure that the data is consistent and complete over a given period. 
  • Machine Learning: In machine learning, the backward fill can ensure that the data is complete and ready for training a model. 


Here is how to use Pandas backward fill from another column: 

Fig : Preview of the output that you will get on running this code from your IDE.

Code

In this solution we're using Pandas library.

Pandas pandas backward fill from another column

PythondotLines of Code : 18dotLicense : Strong Copyleft (CC BY-SA 4.0)

Dependent Libraries : 
>>> import pandas as pd
>>> df = pd.DataFrame({"val1": [9, 2, 9, 1, 5], "val2": [3, None, 4, None, 1]})
>>> df
   val1  val2
0     9   3.0
1     2   NaN
2     9   4.0
3     1   NaN
4     5   1.0
>>> df["val2"].fillna(df["val1"].shift(), inplace=True)
>>> df
   val1  val2
0     9   3.0
1     2   9.0
2     9   4.0
3     1   9.0
4     5   1.0

Instructions

Follow the steps carefully to get the output easily.

  1. Install pandas on your IDE(Any of your favorite IDE).
  2. Copy the snippet using the 'copy' and paste it in your IDE.
  3. Add required dependencies and import them in Python file.
  4. Run the file to generate the output.


I hope you found this useful. I have added the link to dependent libraries, version information in the following sections.


I found this code snippet by searching for 'pandas backward fill from another column' in kandi. You can try any such use case!

Environment Tested

I tested this solution in the following versions. Be mindful of changes when working with other versions.

  1. The solution is created in PyCharm 2021.3.
  2. The solution is tested on Python 3.9.7.
  3. Pandas version-v1.5.2.


Using this solution, we are able to implement backward fill from another column using pandas with simple steps. This process also facilities an easy way to use, hassle-free method to create a hands-on working version of code which would help us to implement backward fill from another column using pandas.

Dependent Library

pandasby pandas-dev

Python doticonstar image 38689 doticonVersion:v2.0.2doticon
License: Permissive (BSD-3-Clause)

Flexible and powerful data analysis / manipulation library for Python, providing labeled data structures similar to R data.frame objects, statistical functions, and much more

Support
    Quality
      Security
        License
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            pandasby pandas-dev

            Python doticon star image 38689 doticonVersion:v2.0.2doticon License: Permissive (BSD-3-Clause)

            Flexible and powerful data analysis / manipulation library for Python, providing labeled data structures similar to R data.frame objects, statistical functions, and much more
            Support
              Quality
                Security
                  License
                    Reuse

                      You can also search for any dependent libraries on kandi like 'pandas'.

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