I want to download data from this webpage
The data can be easily scraped with rvest
.
The code maybe like this :
library(rvest)
library(pipeR)
url <- "http://www.tradingeconomics.com/"
css <- "#ctl00_ContentPlaceHolder1_defaultUC1_CurrencyMatrixAllCountries1_GridView1"
data <- url %>>%
html() %>>%
html_nodes(css) %>>%
html_table()
But there is a problem for webpages like this.
There is a +
button to show the data of all the countries, but the default is just data of 50 countries.
So if I use the code, I can just scrape data of 50 countries.
The +
button is made in javascript
, so I want to know if there is a way in R
to click the button and then scrape the data.
Sometimes it's better to attack the problem at the ajax web-request level. For this site, you can use Chrome's dev tools and watch the requests. To build the table (the whole table, too) it makes a POST
to the site with various ajax-y parameters. Just replicate that, do a bit of data-munging of the response and you're good to go:
library(httr)
library(rvest)
library(dplyr)
res <- POST("http://www.tradingeconomics.com/",
encode="form",
user_agent("Mozilla/5.0 (Macintosh; Intel Mac OS X 10_10_2) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/42.0.2311.50 Safari/537.36"),
add_headers(`Referer`="http://www.tradingeconomics.com/",
`X-MicrosoftAjax`="Delta=true"),
body=list(
`ctl00$AjaxScriptManager1$ScriptManager1`="ctl00$ContentPlaceHolder1$defaultUC1$CurrencyMatrixAllCountries1$UpdatePanel1|ctl00$ContentPlaceHolder1$defaultUC1$CurrencyMatrixAllCountries1$LinkButton1",
`__EVENTTARGET`="ctl00$ContentPlaceHolder1$defaultUC1$CurrencyMatrixAllCountries1$LinkButton1",
`srch-term`="",
`ctl00$ContentPlaceHolder1$defaultUC1$CurrencyMatrixAllCountries1$GridView1$ctl01$DropDownListCountry`="top",
`ctl00$ContentPlaceHolder1$defaultUC1$CurrencyMatrixAllCountries1$ParameterContinent`="",
`__ASYNCPOST`="false"))
res_t <- content(res, as="text")
res_h <- paste0(unlist(strsplit(res_t, "\r\n"))[-1], sep="", collapse="\n")
css <- "#ctl00_ContentPlaceHolder1_defaultUC1_CurrencyMatrixAllCountries1_GridView1"
tab <- html(res_h) %>%
html_nodes(css) %>%
html_table()
tab[[1]]$COUNTRIESWORLDAMERICAEUROPEASIAAUSTRALIAAFRICA
glimpse(tab[[1]]
Another alternative would have been to use RSelenium to go to the page, click the "+" and then scrape the resultant table.