How do I find html_node on search form? - r

Question

I have a list of names (first name, last name, and date-of-birth) that I need to search the Fulton County Georgia (USA) Jail website to determine if a person is in or released from jail.
The website is http://justice.fultoncountyga.gov/PAJailManager/JailingSearch.aspx?ID=400
The site requires you enter a last name and first name, then it gives you a list of results.
I have found some stackoverflow posts that have given me some direction, but I'm still struggling to figure this out. I"m using this post as and example to follow. I am using SelectorGaget to help figure out the CSS tags.
Here is the code I have so far. Right now I can't figure out what html_node to use.
library(rvest)
# Specify URL
fc.url <- "http://justice.fultoncountyga.gov/PAJailManager/JailingSearch.aspx?ID=400"
# start session
jail <- html_session(fc.url)
# Grab initial form
form.unfilled <- jail %>% html_node("form")
form.unfilled
The result I get from form.unfilled is {xml_missing} <NA> which I know isn't right.
I think if I can figure out the html_node value, I can proceed to using set_values and submit_form.
Thanks.

Answer 1

It appears on the initial call the webpage opens onto "http://justice.fultoncountyga.gov/PAJailManager/default.aspx". Once the session is started you should be able to jump to the search page:
library(rvest)
# Specify URL
fc.url <- "http://justice.fultoncountyga.gov/PAJailManager/JailingSearch.aspx?ID=400"
# start session
jail <- html_session("http://justice.fultoncountyga.gov/PAJailManager/default.aspx")
#jump to search page
jail2 <- jail %>% jump_to("http://justice.fultoncountyga.gov/PAJailManager/JailingSearch.aspx?ID=400")
#list the form's fields
html_form(jail2)[[1]]
# Grab initial form
form.unfilled <- jail2 %>% html_node("form")
Note: Verify that your actions are within the terms of service for the website. Many sites do have policy against scraping.

Answer 2

The website relies heavily on Javascript to render itself. When opening the link you provided in a fresh browser instance, you get redirected to http://justice.fultoncountyga.gov/PAJailManager/default.aspx, where you have to click the "Jail Records" link. This executes a bit a Javascript, to send you to the page with the form.
rvest is unable to execute arbitrary Javascript. You might have to look at RSelenium. Selenium basically remote-controls a browser (for example Firefox or Chrome), which executes the Javascript as intended.

Answer 3

Thanks to Dave2e.
Here is the code that works. This questions is answered (but I'll post another one because I'm not getting a table of data as a result.)
Note: I cannot find any Terms of Service on this site that I'm querying
library(rvest)
# start session
jail <- html_session("http://justice.fultoncountyga.gov/PAJailManager/default.aspx")
#jump to search page
jail2 <- jail %>% jump_to("http://justice.fultoncountyga.gov/PAJailManager/JailingSearch.aspx?ID=400")
#list the form's fields
html_form(jail2)[[1]]
# Grab initial form
form.unfilled <- jail2 %>% html_node("form") %>% html_form()
form.unfilled
#name values
lname <- "DOE"
fname <- "JOHN"
# Fille the form with name values
form.filled <- form.unfilled %>%
set_values("LastName" = lname,
"FirstName" = fname)
#Submit form
r <- submit_form(jail2, form.filled,
submit = "SearchSubmit")
#grab tables from submitted form
table <- r %>% html_nodes("table")
#grab a table with some data
table[[5]] %>% html_table()
# resulting text in this table:
# " An error occurred while processing your request.Please contact your system administrator."