Renaming Observations from String in Corresponding Column using R

Introduction

When working with data, it’s common to encounter strings that need to be processed or transformed. One specific task involves renaming observations in a column based on the value of a string in the same row. This article will explore how to achieve this using R, focusing on various techniques and tools available.

Overview of Available Methods

There are several ways to accomplish this task:

1. Using readr::parse_number
2. With sub for extracting the last digit
3. For extracting digits along with characters after ‘+’ and space
4. Using stri_extract_last_regex

Each method will be explained in detail, including examples and illustrations.

Method 1: Using readr::parse_number

The readr::parse_number function from the R package readr is primarily used for parsing numeric values from character strings.

library(readr)
library(dplyr)

# Sample data frame
df <- data.frame(
    PlayerID = c("Hank Aaron + 7", "Babe Ruth + 5", "Ted Williams + 2"),
    Scores = c(90, 85, 80)
)

# Convert the PlayerID column to numeric values by using readr::parse_number
df$PlayerID_num <- df$PlayerID %>% readr::parse_number()

# Display the resulting data frame
print(df)

Output:

Method 2: Using sub for Extracting the Last Digit

The sub function is used to replace substrings in a character vector. This method can be applied to extract the last digit from a string.

library(dplyr)

# Sample data frame
df <- data.frame(
    PlayerID = c("Hank Aaron + 7", "Babe Ruth + 5", "Ted Williams + 2"),
    Scores = c(90, 85, 80)
)

# Convert the PlayerID column to numeric values by using sub
df$PlayerID_num <- df$PlayerID %>% 
    sub(".*\\+\\s*(\\d+)$", "\\1")

# Display the resulting data frame
print(df)

Output:

Method 3: Extracting Digits Along with Characters After ‘+’ and Space

The same sub function can be used to extract the digits along with characters after ‘+’ and space. This approach includes the entire match, including non-numeric values.

library(dplyr)

# Sample data frame
df <- data.frame(
    PlayerID = c("Hank Aaron + 7", "Babe Ruth + 5", "Ted Williams + 2"),
    Scores = c(90, 85, 80)
)

# Convert the PlayerID column to numeric values by using sub
df$PlayerID_num <- df$PlayerID %>% 
    sub(".*\\+\\s*(\\d+\\D*)$", "\\1")

# Display the resulting data frame
print(df)

Output:

Method 4: Using stri_extract_last_regex

The stri_extract_last_regex function from the R package stringi is a powerful tool for extracting substrings that match a given pattern. This method can be applied to extract digits along with characters after ‘+’ and space.

library(stringi)
library(dplyr)

# Sample data frame
df <- data.frame(
    PlayerID = c("Hank Aaron + 7", "Babe Ruth + 5", "Ted Williams + 2"),
    Scores = c(90, 85, 80)
)

# Convert the PlayerID column to numeric values by using stri_extract_last_regex
library(stringi)
df$PlayerID_num <- df$PlayerID %>% 
    stri_extract_last_regex("\\d+\\D*$")

# Display the resulting data frame
print(df)

Output:

Conclusion

In conclusion, there are multiple methods to rename observations from a string in the same row. The choice of method depends on the specific use case and desired output.

Using readr::parse_number is useful when the string contains only numeric values. For strings that contain non-numeric characters, either sub, stri_extract_last_regex, or other similar functions may be used to extract the necessary information.

The code snippets provided demonstrate each method’s functionality with sample data frames.

Last modified on 2024-07-05