“ XML内容似乎不是XML”：R中xmlTreeParse中的错误

Question

I am going through the topicmodels tutorial in R. Around page 12, they strip HTML tags and Greek letters:

R> library("XML")
R> remove_HTML_markup <- function(s) {
+ doc <- htmlTreeParse(s, asText = TRUE, trim = FALSE)
+ xmlValue(xmlRoot(doc))
+ }
R> remove_HTML_markup(JSS_papers[1,"description"])
Error: XML content does not seem to be XML, nor to identify a file name ...

JSS_papers stores metadata related to a collection of papers downloaded from a journal. The entry under the description tag is the abstract of the article. This one doesn't have any tags:

JSS_papers[1,"description"] = "The fit of a variogram model to spatially-distributed 
    data is often difficult to assess. A graphical diagnostic written in S-plus is   
    introduced that allows the user to determine both the general quality of the fit of a 
    variogram model, and to find specific pairs of locations that do not have measurements 
    that are consonant with the fitted variogram. It can help identify nonstationarity,    
    outliers, and poor variogram fit in general. Simulated data sets and a set of soil      
    nitrogen concentration data are examined using this graphical diagnostic."

Answer 1

I had this same problem recently. The variable that I had assigned with the URL had a typo in it. Double-check your variable, s, and see if there's something wrong there.