Retrieve user comments from an individual PTT post

get_post_comment returns a data frame with n rows and 5 cols, where n is the number of comments in the post.

get_post_comment(post_xml)

Arguments

post_xml	`xml_document` created by `read_html2` or `read_html` See `read_html` for details.

A data frame with n rows and 5 variables:

tag: tag of the comment, can be one of the 3 values: Push corresponds to "推", Boo corresponds to "噓", and Neu corresponds to "bu 推 bu 噓"
user: ID of the user who left the comment.
comment: The content of the comment.
ip: ip address of the comment.
time: The comment date time.

#url <- "https://www.ptt.cc/bbs/Gossiping/M.1534415307.A.BE5.html"
#post <- read_html2(url)

#get_post_comment(post)