使用R網絡抓取數據

Question

目標：我試圖從網頁http://www.nepalstock.com/datanepse/previous.php中取消所有公司的歷史日常股票價格。以下代碼有效;但是，它只會生成最近（2015年2月5日）日期的每日股價。換句話說，輸出是一樣的，不管我輸入的日期如何。如果你能在這方面提供幫助，我將不勝感激。

library(RHTMLForms) 
    library(RCurl) 
    library(XML) 
    url <- "http://www.nepalstock.com/datanepse/previous.php" 
    forms <- getHTMLFormDescription(url) 

    # we are interested in the second list with date forms 
    # forms[[2]] 
    # HTML Form: http://www.nepalstock.com/datanepse/ 
    # Date: [ ] 

    get_stock<-createFunction(forms[[2]]) 

#create sequence of dates from start to end and store it as a list 

    date_daily<-as.list(seq(as.Date("2011-08-24"), as.Date("2011-08-30"), "days")) 

# determine the number of elements in the list 

    num<-length(date_daily) 

    daily_1<-lapply(date_daily,function(x){ 
     show(x) #displays the particular date 
     readHTMLTable(htmlParse(get_stock(Date = x)), which = 7) 

    }) 


#18 tables out of which 7 is one what we desired 

# change the colnames 

    col_name<-c("SN","Traded_Companies","No_of_Transactions","Max_Price","Min_Price","Closing_Price","Total_Share","Amount","Previous_Closing","Difference_Rs.") 
    daily_2<-lapply(daily_1,setNames,nm=col_name) 

Output: 
> head(daily_2[[1]],5) 
SN         Traded_Companies No_of_Transactions Max_Price Min_Price Closing_Price Total_Share Amount 
1 1     Agricultural Development Bank Ltd     24  489  471   473  2,868 1,359,038 
2 2 Arun Valley Hydropower Development Company Limited     40  365  360   362  8,844 3,199,605 
3 3     Alpine Development Bank Limited     11  297  295   295   150 44,350 
4 4     Asian Life Insurance Co. Limited     10  1,230  1,215   1,225   898 1,098,452 
5 5       Apex Development Bank Ltd.     23  131  125   131  6,033 769,893 
    Previous_Closing Difference_Rs. 
1    480    -7 
2    363    -1 
3    303    -8 
4   1,242   -17 
5    132    -1 
> tail(daily_2[[1]],5) 
    SN     Traded_Companies No_of_Transactions Max_Price Min_Price Closing_Price Total_Share Amount Previous_Closing 
140 140    United Finance Ltd     4  255  242   242   464 115,128    255 
141 141 United Insurance Co.(Nepal)Ltd.     3  905  905   905   234 211,770    915 
142 142   Vibor Bikas Bank Limited     7  158  152   156   710 109,510    161 
143 143 Western Development Bank Limited     35  320  311   313  7,631 2,402,497    318 
144 144 Yeti Development Bank Limited     22  139  132   139  14,355 1,921,511    134 
    Difference_Rs. 
140   -13 
141   -10 
142    -5 
143    -5 
144    5 

Answer 1

這裏有一個快速的方法。請注意，該站點使用POST請求將日期發送到服務器。

library(rvest) 
library(httr) 

page <- "http://www.nepalstock.com/datanepse/previous.php" %>% 
    POST(body = list(Date = "2015-02-01")) %>% 
    html() 

page %>% 
    html_node(".dataTable") %>% 
    html_table(header = TRUE)