Скачать или смотреть Cumulatively Add Numbers Between Rows to Create New Columns in R

Learn how to cumulatively add numbers between rows in R to create new columns in your dataframe using the `tidyverse`. This step-by-step guide explains the process clearly.
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Cumulatively Add Numbers Between Rows to Create New Columns in R

If you're working with data in R and need to create new columns by cumulatively adding numbers between rows in a dataframe, you're in the right place. This post will guide you through the process step-by-step, using a practical example.

The Problem

Suppose you have a dataframe that looks like this:

[[See Video to Reveal this Text or Code Snippet]]

You want to add two new columns—new_start and new_end—where each value is calculated based on previous rows. For the first row, new_start and new_end remain the same. For subsequent rows, the calculations change slightly depending on the Sp1 values.

Expected Results

After performing the necessary calculations, the expected output should look similar to this:

[[See Video to Reveal this Text or Code Snippet]]

The Solution

The solution utilizes the tidyverse package in R, which includes powerful functions for data manipulation. To achieve the cumulative addition, follow these steps:

Step-by-Step R Code

Load the required libraries (if you haven't already):

[[See Video to Reveal this Text or Code Snippet]]

Use the mutate function to create the new columns:

[[See Video to Reveal this Text or Code Snippet]]

Explanation of the Code

mutate: This function is used to create or transform columns in your dataframe.

new_end Calculation:

You start with start[1] - 1 to position your cumulative addition correctly.

cumsum(end + 1) gives you the cumulative sum of ends, with an additional 1 added.

cumsum(start) subtracts the total of starting points up to that row, creating a running total.

new_start Calculation:

lag(new_end, default = start[1] - 1) shifts the previous new_end values down for the new calculation.

You add 1 to ensure that you're capturing the starting point of the next row.

Final Output

After running the above code, your dataframe will look as follows:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By following these steps, you can effectively and efficiently create new columns in your dataframe based on cumulative calculations of existing data. The tidyverse suite makes these operations easy and intuitive, allowing you to focus on your analysis rather than complex coding.

For any further questions or clarifications, feel free to reach out!