Question

我正在从网上抓取数据来做自己的小项目。我的目标是浏览每一个页面（按月和年划分），每天进行一次，并进行多少次呼叫。我从一个空白的数据框开始，然后附加我继续进行的每个月的通话日期和次数。

问题是...当我将行绑定在一起时，日期变成了数字。我该如何解决？（如果我只运行一列代码，则日期格式正确。）

问题将在代码的最后一部分，但我提供了其他内容作为参考。

#Scrapes dates from the police call map
#ex: "Tuesday, Sept. 30"
get_date <- function(url,year){
  read_html(url) %>%
    html_nodes('.bull li a') %>%      
    html_text() %>% 
    str_trim() %>%                       
    unlist() %>%
   #adds the current year to the end
    paste(year)
}

#Scrapes number of calls for each day.
#ex: "262 calls for service"
get_num_calls <- function(url){
  read_html(url) %>%
    html_nodes('.bull b') %>%      
    html_text() %>% 
    str_trim() %>%                       
    unlist()  %>%
    #Parse number is here to eliminate the "calls for service" text
    parse_number()
}

#This function converts date to proper POSIXct format.

convert <- function(date,month,year){
  if (month %in% abbr) {
    parse_date_time(date, orders = "%A, %b. %d %Y")

  } else if (month %in% full) {
    parse_date_time(date, orders = "%A, %B. %d %Y")

  } else {
    #September is not in an accepted format, so it needs to be changed.
    date <- sub("Sept.", "Sep.", date)
    parse_date_time(date, orders = "%A, %b. %d %Y")

  }
}

#years and months to cycle through the URLs
years <- as.character(2009:2018)

months <- c("jan", "feb","mar","apr", "may", "jun",
            "jul", "aug", "sep", "oct", "nov", "dec")

#months that are abbreviated in the data.
abbr <- c("jan", "feb", "aug", "oct", "nov", "dec")

#months that are NOT abbreviated in the data.
full <- c("mar", "april", "may", "jun", "jul")

#url_base will have "month/year/" added to the end in the loop
url_base <- "http://projects.registerguard.com/police/eugene/"

#No matter which of these I use, it doesn't work properly.
Police <- c()

Police <- data.frame(date = as.POSIXct(date(), origin = lubridate::origin),
                     calls = integer())

for (year in years){
  for (month in months){
    url <- paste(url_base, year, '/', month, '/', sep = "")
    date <- get_date(url,year)
    date <- convert(date,month,year)
    calls <- get_num_calls(url)
    new <- cbind(date, calls)
    Police <- rbdf(Police, new)
  }
}

POSIXct行无法正确绑定

0 个答案: