In f0nzie/petroleum.ml: Machine Learning Applications in Machine Learning

Problem with keyword combination

Error in open.connection(x, "rb") : HTTP error 500.
Warning in .Internal(exists(x, envir, mode, inherits)) :
  closing unused connection 3 (https://www.onepetro.org/search?q="machine+learning"AND"economics"AND"GPR"&peer_reviewed=&published_between=&from_year=&to_year=&dc_type=conference-paper&start=-1000&rows=1000)

30     1 'machine+learning'AND'economics'AND'GPR'  
Error in open.connection(x, "rb") : HTTP error 500.
12.open.connection(x, "rb")
11.open(x, "rb")
10.read_xml.connection(con, encoding = encoding, ..., as_html = as_html, base_url = x, options = options)
9.read_xml.character(x, encoding = encoding, ..., as_html = TRUE, options = options)
8.read_xml(x, encoding = encoding, ..., as_html = TRUE, options = options)
7.withCallingHandlers(expr, warning = function(w) invokeRestart("muffleWarning"))
6.suppressWarnings(read_xml(x, encoding = encoding, ..., as_html = TRUE, options = options))
5.read_html.default(url)
4.read_html(url) at papers_to_dataframe.R#17
3.onepetro_page_to_dataframe(url) at multipage.R#65
2.read_multipage(url.2, doctype = "conference-paper") at joining.R#50
1.join_keywords(major, discipline, ml_technique.1, get_papers = TRUE, sleep = 3)

library(petro.One)

major <- c("machine learning")
discipline <- c("economics")
ml_technique.1 <- c("GPR", "Gaussian Process Regression",
                    "PCA", "principal component analysis"
                                        )
by.ml_technique.1 <- join_keywords(major, discipline, ml_technique.1, 
                                   get_papers = TRUE, sleep = 3, verbose = TRUE)

by.ml_technique.1