如何基于字符串模式生成完整的分页URL

现有如下R语言数据框，其中的URL分属两个不同主题（thee-t119532和thee-t143332），分页遵循s-0、s-10、s-20……的规律，但部分主题仅包含部分分页链接，需要补全所有缺失的分页，生成包含全部分页的完整数据框。

原始数据框 #

df <- data.frame(url = c("https://tapatalk.com/groups/thee-t119532-s0.html?sid=674002291c431ba23dd69c34e8a20217",
      "https://tapatalk.com/groups/thee-t119532-s50.html?sid=674002291c431ba23dd69c34e8a20217",
      "https://tapatalk.com/groups/thee-t119532-s60.html?sid=674002291c431ba23dd69c34e8a20217",
      "https://tapatalk.com/groups/thee-t119532-s70.html?sid=674002291c431ba23dd69c34e8a20217","https://tapatalk.com/groups/thee-t143332-s0.html?sid=674002291c431ba23dd69c34e8a20217",
      "https://tapatalk.com/groups/thee-t143332-s30.html?sid=674002291c431ba23dd69c34e8a20217"),
    page_id=c("0","50","60","70","0","30"))

目标完整数据框 #

df_full <- data.frame(url = c("https://tapatalk.com/groups/thee-t119532-s0.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s10.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s20.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s30.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s40.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s50.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s60.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t119532-s70.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t143332-s0.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t143332-s10.html?sid=674002291c431ba23dd69c34e8a20217",
"https://tapatalk.com/groups/thee-t143332-s20.html?sid=674002291c431ba23dd69c34e8a20217",
      "https://tapatalk.com/groups/thee-t143332-s30.html?sid=674002291c431ba23dd69c34e8a20217"),
page_id=c("0","10","20","30","40","50","60","70","0","10","20","30"))

解决方案 #

借助tidyverse工具包（dplyr处理数据，stringr处理字符串）完成，步骤如下：

1. 加载依赖包

library(tidyverse)

2. 拆分URL关键信息
   从原始URL中提取主题标识、URL固定前缀/后缀，同时转换分页ID为数值类型：

df_processed <- df %>%
  mutate(
    # 提取主题ID（如thee-t119532）
    topic_id = str_extract(url, "thee-t\\d+"),
    # 提取URL固定前缀（到主题ID后、分页前）和后缀（sid参数部分）
    url_prefix = str_replace(url, "(thee-t\\d+)-s\\d+\\.html(\\?sid=.*)", "\\1-s"),
    url_suffix = str_extract(url, "\\?sid=.*")
  ) %>%
  mutate(page_id = as.numeric(page_id))

3. 生成全部分页并拼接URL
   按主题分组，生成从0到最大分页、步长为10的完整分页序列，再拼接成完整URL：

df_full <- df_processed %>%
  group_by(topic_id, url_prefix, url_suffix) %>%
  summarise(
    max_page = max(page_id),
    # 生成完整分页序列
    page_id = seq(from = 0, to = max_page, by = 10),
    .groups = "drop"
  ) %>%
  # 拼接完整URL
  mutate(
    url = str_c(url_prefix, page_id, ".html", url_suffix),
    page_id = as.character(page_id)
  ) %>%
  # 匹配目标数据框列顺序
  select(url, page_id)

执行后，df_full即为包含全部分页的完整数据框，与目标结果一致。

内容的提问来源于stack exchange，提问作者sd3184