如何在R中将宠物年龄字符串（周/月/年）转换为年数值？

Hey there! Let's turn those messy age strings into clean, numeric years using the tidyverse tools you already know—no confusing loops needed. Here's a straightforward approach tailored to your familiarity with mutate() and friends:

Step 1: Load the Tidyverse #

First, make sure you've got the package loaded (since you mentioned knowing mutate() and filter(), you probably already do, but just in case):

library(tidyverse)

Step 2: Extract Numeric Values and Units #

We'll use stringr functions (part of tidyverse) to pull out the number and the unit from each age string. Then we'll convert the number to numeric format:

pet_adoptions <- pet_adoptions %>%
  mutate(
    # Grab the numeric part of the age string
    age_number = as.numeric(str_extract(age, "\\d+")),
    # Grab the text unit (like "months" or "years")
    age_unit = str_extract(age, "[a-zA-Z]+")
  )

• str_extract(age, "\\d+") finds all digits in the age column and pulls them out.
• str_extract(age, "[a-zA-Z]+") grabs the letters (the unit part) from the string.

Step 3: Convert Units to Years with case_when() #

Instead of messy conditional statements, case_when() lets us write clear, readable rules for converting each unit to years. This is perfect for tidy workflows:

pet_adoptions_clean <- pet_adoptions %>%
  mutate(
    age_years = case_when(
      # If the unit includes "year", keep the number as-is
      str_detect(age_unit, "year") ~ age_number,
      # Convert months to years (divide by 12)
      str_detect(age_unit, "month") ~ age_number / 12,
      # Convert weeks to years (divide by ~52 weeks in a year)
      str_detect(age_unit, "week") ~ age_number / 52,
      # Add a rule for days if you have them (divide by 365)
      str_detect(age_unit, "day") ~ age_number / 365,
      # For any unrecognized units, return NA (you can adjust this if needed)
      TRUE ~ NA_real_
    )
  ) %>%
  # Optional: Remove the intermediate columns if you don't need them
  select(-age_number, -age_unit)

• str_detect() works like grepl()—it checks if the unit string contains the keyword (e.g., "year" matches both "year" and "years", which covers plural cases!).
• case_when() evaluates each condition in order, so make sure your rules are ordered logically.

Example Output #

If your original age column looks like this:

The final age_years column will be:

That's it! This approach stays true to the tidyverse style you're comfortable with, and avoids the need for complex loops. If you have other edge cases (like "1 year and 6 months"), we can adjust the code, but this should handle the main cases you mentioned.

内容的提问来源于stack exchange，提问作者Elizabeth Robinson