Question

以下代码用于通过API调用对网站进行网页剪贴。我只需要更改startDate和endDate即可获取所需的数据集。以前它可以正常工作，可以很好地执行其循环，但是在对html_nodes（）部分进行了一些修改之后-尝试提取网页中的不同部分，它会一直返回相同日期的数据。带有错误警告“ seq.int（0，to0-from，by）中存在错误：r中'by'参数的错误登录。在这里应该做什么？

library(tidyverse)
library(readr)
library(tidyr)
library(dplyr)
library(xlsx)
library(beepr)

get_sounding_data <- function(region = c("naconf", "samer", "pac", "nz", "ant",
                                     "np", "europe", "africa", "seasia", "mideast"),
                          date,
                          from_hr = c("00", "12", "all"),
                          to_hr = c("00", "12", "all"),
                          station_number = 48615) {

  # we use these pkgs (the readr and dplyr dependencies removed)
  suppressPackageStartupMessages({
    require("xml2", quietly = TRUE)
    require("httr", quietly = TRUE)
    require("rvest", quietly = TRUE)
  })

  # validate region
  region <- match.arg(
    arg = region,
    choices = c(
      "naconf", "samer", "pac", "nz", "ant",
      "np", "europe", "africa", "seasia", "mideast"
    )
  )

  # validates the date for us if it's a character string
  date <- as.Date(date)

  # get year and month
  year <- as.integer(format(date, "%Y"))
  stopifnot(year %in% 1973:as.integer(format(Sys.Date(), "%Y")))

  year <- as.character(year)
  month <- format(date, "%m")

# we need these to translate day & *_hr to the param the app needs
c(
"0100", "0112", "0200", "0212", "0300", "0312", "0400", "0412",
"0500", "0512", "0600", "0612", "0700", "0712", "0800", "0812",
"0900", "0912", "1000", "1012", "1100", "1112", "1200", "1212",
"1300", "1312", "1400", "1412", "1500", "1512", "1600", "1612",
"1700", "1712", "1800", "1812", "1900", "1912", "2000", "2012",
"2100", "2112", "2200", "2212", "2300", "2312", "2400", "2412",
"2500", "2512", "2600", "2612", "2700", "2712", "2800", "2812",
"2900", "2912", "3000", "3012", "3100", "3112"
  ) -> hr_vals

c(
"01/00Z", "01/12Z", "02/00Z", "02/12Z", "03/00Z", "03/12Z", "04/00Z",
"04/12Z", "05/00Z", "05/12Z", "06/00Z", "06/12Z", "07/00Z", "07/12Z",
"08/00Z", "08/12Z", "09/00Z", "09/12Z", "10/00Z", "10/12Z", "11/00Z",
"11/12Z", "12/00Z", "12/12Z", "13/00Z", "13/12Z", "14/00Z", "14/12Z",
"15/00Z", "15/12Z", "16/00Z", "16/12Z", "17/00Z", "17/12Z", "18/00Z",
"18/12Z", "19/00Z", "19/12Z", "20/00Z", "20/12Z", "21/00Z", "21/12Z",
"22/00Z", "22/12Z", "23/00Z", "23/12Z", "24/00Z", "24/12Z", "25/00Z",
"25/12Z", "26/00Z", "26/12Z", "27/00Z", "27/12Z", "28/00Z", "28/12Z",
"29/00Z", "29/12Z", "30/00Z", "30/12Z", "31/00Z", "31/12Z"
  ) -> hr_inputs

  hr_trans <- stats::setNames(hr_vals, hr_inputs)

  o_from_hr <- from_hr <- as.character(tolower(from_hr))
  o_to_hr <- to_hr <- as.character(tolower(to_hr))

  if ((from_hr == "all") || (to_hr == "all")) {
  from_hr <- to_hr <- "all"
  } else {

  from_hr <- hr_trans[sprintf("%s/%02dZ", format(date, "%d"), as.integer(from_hr))]
match.arg(from_hr, hr_vals)

 to_hr <- hr_trans[sprintf("%s/%02dZ", format(date, "%d"), as.integer(to_hr))]
match.arg(to_hr, hr_vals)
 }

  # clean up the station number if it was entered as a double
  station_number <- as.character(as.integer(station_number))

# execute the API call
httr::GET(
url = "http://weather.uwyo.edu/cgi-bin/sounding",
query = list(
  region = region,
  TYPE = "TEXT:LIST",
  YEAR = year,
  MONTH = sprintf("%02d", as.integer(month)),
  FROM = from_hr,
  TO = to_hr,
  STNM = station_number
   )
  ) -> res

  # check for super bad errors (that we can't handle nicely)
  httr::stop_for_status(res)

  # get the page content
  doc <- httr::content(res, as="text")

  # if the site reports no data, issue a warning and return an empty data frame
  if (grepl("Can't get", doc)) {
    doc <- xml2::read_html(doc)
    msg <- rvest::html_nodes(doc, "body")
    msg <- rvest::html_text(msg, trim=TRUE)
    msg <- gsub("\n\n+.*$", "", msg)
    warning(msg)
    return(data.frame(stringsAsFactors=FALSE))
   }

  # if the site reports no data, issue a warning and return an empty data frame
  if (grepl("Can't get", doc)) {
    doc <- xml2::read_html(doc)
    msg <- rvest::html_nodes(doc, "body")
    msg <- rvest::html_text(msg, trim=TRUE)
    msg <- gsub("\n\n+.*$", "", msg)
    warning(msg)
    return(data.frame(stringsAsFactors=FALSE))
   }

  # turn it into something we can parse
  doc <- xml2::read_html(doc)

  raw_dat <- doc %>%
    html_nodes("h3+ pre") %>% 
    html_text()

  indices <- raw_dat %>% 
    str_split(pattern = "\n", simplify = T) %>% 
    map_chr(str_squish) %>% 
    tibble(x = .) %>% 
    separate(x, into = c("Station", "Value"), sep = ": ") %>% 
    filter(!is.na(Value))

  data <- tidyr::spread(indices, Station, Value)
  data
    }

startDate <- as.Date("01-11-1979", format="%d-%m-%y")
endDate <- as.Date("31-01-1980",format="%d-%m-%y")

days <- seq(startDate, endDate, "1 day")

lapply(days[1:92], function(day) {
  get_sounding_data(
    region = "seasia",
    date = day,
    from_hr = "00",
    to_hr = "00",
    station_number = "48615"
  )
}) -> soundings_48615

warnings()

new_df <- map(soundings_48615, . %>% mutate_all(parse_guess))
dat <- bind_rows(new_df)
dat <- dat %>% separate(col =`Observation time`, into = c('Date', 'time'), sep = '/')

dat$Date <- as.Date(dat$Date, format = "%y%m%d")

#save in text file
write.csv(dat, 'c:/Users/Hp/Documents/yr/climatology/yr_SoundingIndexLowerPart/1979.csv')

get_sounding_data <- NULL
beep()

Answer 1

您现在遇到的错误似乎是基于日期格式的。以下时间更具体

as.Date("01-11-1979", format="%d-%m-%y")
as.Date("31-01-1980",format="%d-%m-%y")

输出

"2019-11-01"
"2019-01-31"

R的日期/时间格式是国际标准yyyy-mm-dd。因此，"2019-11-01"在时间"2019-01-31"之后出现。这样，如果尝试一次迭代1个正日，这将导致序列失败。格式化是这里的问题，要解决的问题是有一个非常简单的解决方案。始终使用国际标准日期格式，因为（几乎）所有程序都可以识别这些格式。

因此，将代码的日期序列部分更改为

....
startDate <- as.Date("1979-11-01")
endDate <- as.Date("1980-01-31")

days <- seq(startDate, endDate, "1 day")
....

请注意格式更改。至于为什么它将1979年更改为2019年，我不完全确定，对于这种奇怪的行为，其他人可能会有更复杂的答案。

seq.int（0，to0-from，by）中的错误是什么意思：r中'by'参数的错误符号

1 个答案: