Web Scraping in R to extract data from multiple pages

Question

I am trying to read in the table displaying market cap details on https://stockanalysis.com/stocks/

The code below reads only the first 500 observations because the website that it is reading from displays only 500 on the first page.

Need help identifying which HTML elements I need to use to be able to extract data from all pages. Here I use the 'symbol-table' object thanks to Vishal A

library(rvest)
library(dplyr)
url <- ("https://stockanalysis.com/stocks/")

page <- read_html(url)

stocks <- page %>%
  html_nodes('table#symbol-table') %>%
  html_table() %>% .[[1]]
stocks

user_6241235 · Answer

Observations:

If you scroll down the page you will see there is an option to request more results in a batch. In this particular case, setting to the maximum batch size returns all results in one go.

Monitoring the web traffic shows no additional traffic when requesting more results meaning the data is present in the original response.

Doing a search of the page source for the last symbol reveals the all the items are pre-loaded in a script tag. Examining the JavaScript source files shows the instructions for pushing new batches onto the page based on various input params.

Solution:

You can simply extract the JavaScript object from the script tag and parse as JSON. Convert the list of lists to a dataframe then add in a constructed url based on common base string + symbol.

TODO:

Up to you if you wish to update header names
You may wish to format the numeric column to match webpage format

R:

library(rvest)
library(jsonlite)
library(tidyverse)

r <- read_html('https://stockanalysis.com/stocks/') %>% 
  html_element('#__NEXT_DATA__') %>% 
  html_text() %>% 
  jsonlite::parse_json()

df <- map_df(r$props$pageProps$stocks,  ~ .x)%>%
      mutate(url = paste0('https://stockanalysis.com/stocks/', s))

Sample output:

Web Scraping in R to extract data from multiple pages

1 Answers