get_temp_4digits.R

#########################################################
#########################################################
#
# 気象庁＞各種データ・資料 > 過去の気象データ検索
#   https://www.data.jma.go.jp/obd/stats/etrn/index.php
#
#########################################################

pacman::p_load( 
  conflicted,
  tidyverse,
  rvest,
  polite,
  janitor,
  RcppRoll,
  here)


#
# functions
#

get_temp_data <- function(URL) {
  URL |>
    bow() |>
    scrape(content = "text/html; charset=UTF-8") |> 
    html_table() |> 
    pluck(6) |>
    clean_names() |>
    select(ri, jiang_shui_liang, 
           qi_wen, qi_wen_2, qi_wen_3, ri_zhao_shi_jian_h) |> 
    slice(-(1:2)) |> 
    dplyr::mutate_all(~gsub(.,pattern="]",replacement = "")) |> 
    dplyr::mutate_all(~gsub(.,pattern=")",replacement = "")) |> 
    mutate(
      day = ri |> as.integer(),
      precipitation = jiang_shui_liang |> as.double(),
      mean_temp = qi_wen |> as.double(),
      max_temp = qi_wen_2 |> as.double(),
      min_temp = qi_wen_3 |> as.double(),
      sunshine = ri_zhao_shi_jian_h |> as.double(),
      .keep = "none")
}


multiple_years <- function(base_url, year_range, month_range) {
  year_month_range <- crossing(year_range, month_range)
  
  paste0(base_url, year_month_range$year_range, "&month=", year_month_range$month_range, "&day=&view=p1") |>
    map(\(url) get_temp_data(url), .progress = TRUE) |>
    list_rbind(names_to = "rowid") |> 
    left_join(
      year_month_range |>
        rowid_to_column(),
      by = join_by(rowid)) |>
    select(!rowid) |> 
    mutate(age = paste0(floor(year_range / 10) * 10, "s")) |>
    rename(year = year_range, month = month_range)
}

########################################################################
#
# Example: 千葉県 坂畑（block_no=1241）　1978年1月～
#

url1 <- "https://www.data.jma.go.jp/obd/stats/etrn/view/daily_a1.php?prec_no=45"
url2 <- "&block_no=1241"
url3 <- "&year="

base_url <- paste0(url1, url2, url3)
year_range <- 1978:2023
month_range <- 1:12

sakahata_1978_2023 <- multiple_years(base_url, year_range, month_range)


save(sakahata_1978_2023, 
     file = here("data", "sakahata_1978_2023.RData"))