Extract link texts and urls from a web page into an R data frame

scraplinks.R

#' Extract link texts and urls from a web page
#' @param url character an url
#' @return a data frame of link text and urls
#' @examples
#' \dontrun{
#' scraplinks("http://localhost/")
#' glinks <- scraplinks("http://google.com/")
#' }
#' @export
scraplinks <- function(url){
    # Create an html document from the url
    webpage <- xml2::read_html(url)
    # Extract the URLs
    url_ <- webpage %>%
        rvest::html_nodes("a") %>%
        rvest::html_attr("href")
    # Extract the link text
    link_ <- webpage %>%
        rvest::html_nodes("a") %>%
        rvest::html_text()
    return(tibble(link = link_, url = url_))
}

@ajatoledo the dplyr::data_frame has been replaced with dplyr::tibble you probably have seen the message: "data_frame() is deprecated, use tibble()." I replaced this in the function above.

@paulrougieux data.frame() != data_frame(); my suggestion returns a data frame, tibble returns a tibble. Approach is yours, but data.frame() is base R while tibble() is tidyverse.

@ajatoledo data.frame creates factor variables by default, you should add the argument stringsAsFactors=FALSE to have character variables: data.frame(link = link_, url = url_, stringsAsFactors=FALSE). tibble(link = link_, url = url_) is preferable in this simple example, because it will creates the link and url columns as character variables. In addition rvest is also part of the tidyverse suite of packages, and of course tibble is loaded by default by the very well known dplyr package.

@paulrougieux missed the dplyr items for url and link items meaning tibble() is already in the namespace; however, the description says it outputs into a data frame, which could be misleading as the returned object is a tibble. Which could be problematic for some users as tibble doesn't always play well with other functions that expect data.frame inputs, e.g. write.csv().

As for stringsAsFactors=FALSE in data.frame; if you wanted to set that, you'd likely want to do that in the initial function arguments so user is stuck to pre-defined arguments in the function.

Though either way, do what you want, each use case is different. Either way, the original function provided me a starting point when I needed it and got me where I needed.

@paulrougieux;
Hi Paul,
I want to use this code but I first need to get into a link href=database.htm in the main page of the website. And then I have to extract information from many more links there.
How do I modify this code accordingly?
Thanks.

@goodyonsen you will have better luck asking on Stackoverflow. To get you started, prepare answers to the following questions. What have you tried so far? What is the error message? Make a reproducible example with a public URL.