Reshape Data: Concatenate

Problem Description

You are given two DataFrames, df1 and df2, with the same structure. Your task is to concatenate these two DataFrames vertically into one DataFrame.

Key Insights

• Both DataFrames have the same column names and types.
• The vertical concatenation implies stacking the rows of df2 below those of df1.
• The resulting DataFrame should maintain the order of the rows as they appear in both DataFrames.

Space and Time Complexity

Time Complexity: O(n + m), where n is the number of rows in df1 and m is the number of rows in df2. This is because we need to iterate through both DataFrames to merge them.

Space Complexity: O(n + m) for storing the combined DataFrame, as we need space for all the rows from both DataFrames.

Solution

To concatenate two DataFrames vertically, we can utilize the built-in functionality of DataFrame libraries (such as pandas in Python). The algorithm involves:

1. Utilize the concat function, which can take a list of DataFrames and concatenate them along a specified axis (in this case, rows).
2. Ensure that the two DataFrames have the same columns so that the resulting DataFrame is structured correctly.

Code Solutions