XML剖析

原則上，XML的剖析和HTML的剖析是一樣的，但是XML有NameSpace的概念如<media:group>，會使得Element看起來很像帶有Pseudo-Class。此時，如果你把他整個media:group當成CSS Selector的目標一定會選不到。因為media只是namespace而已。這時候你只需要打namespace後面那個字即可，例如下方的group、title、content、community。

<media:group>
<media:title>20201029行政院會後記者會（第3724次會議）</media:title>
<media:content url="https://www.youtube.com/v/BRHoFtStxPE?version=3" type="application/x-shockwave-flash" width="640" height="390"/>
<media:thumbnail url="https://i3.ytimg.com/vi/BRHoFtStxPE/hqdefault.jpg" width="480" height="360"/>
<media:description>【主持】 行政院發言人 丁怡銘 【出席】 經濟部次長 林全能 內政部次長 花敬群 【報告一】經濟部：「推動振興消費措施現階段成果」 懶人包→https://reurl.cc/A8pOVj 【討論一】內政部「中華民國專屬經濟海域及大陸礁層法」第18條修正草案及經濟部「土石採取法」第36條修正草案 內政部懶人包→https://reurl.cc/Md9XQ3 經濟部懶人包→https://reurl.cc/0OQprA 法條→https://reurl.cc/bRq2pv</media:description>
<media:community>
<media:starRating count="3" average="5.00" min="1" max="5"/>
<media:statistics views="362"/>
</media:community>
</media:group>

範例：Youtube RSS

rss_url <- str_c("https://www.youtube.com/feeds/videos.xml?channel_id=",
                 channel_id)

entry.nodes <- rss_url %>%
    read_html() %>%
    html_nodes("entry")

vid = entry.nodes %>% xml_node("videoid") %>% html_text()
title = entry.nodes %>% html_node("title") %>% html_text()
link = entry.nodes %>% html_node("link") %>% html_attr("href")
published  = entry.nodes %>% html_node("published") %>% html_text() %>%
    ymd_hms(tz = "Asia/Taipei")
description = entry.nodes %>% html_node("group description") %>% html_text() %>% trimws()
views = entry.nodes %>% html_node("group community statistics") %>% html_attr("views")

video_rss.tb <- tibble(vid = vid, title = title, link = link,
             published = published, description = description, views = views)

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<media:group> <media:title>20201029行政院會後記者會（第3724次會議）</media:title> <media:content url="https://www.youtube.com/v/BRHoFtStxPE?version=3" type="application/x-shockwave-flash" width="640" height="390"/> <media:thumbnail url="https://i3.ytimg.com/vi/BRHoFtStxPE/hqdefault.jpg" width="480" height="360"/> <media:description>【主持】行政院發言人丁怡銘【出席】經濟部次長林全能內政部次長花敬群【報告一】經濟部：「推動振興消費措施現階段成果」懶人包→https://reurl.cc/A8pOVj 【討論一】內政部「中華民國專屬經濟海域及大陸礁層法」第18條修正草案及經濟部「土石採取法」第36條修正草案內政部懶人包→https://reurl.cc/Md9XQ3 經濟部懶人包→https://reurl.cc/0OQprA 法條→https://reurl.cc/bRq2pv</media:description> <media:community> <media:starRating count="3" average="5.00" min="1" max="5"/> <media:statistics views="362"/> </media:community> </media:group>

範例：Youtube RSS

rss_url <- str_c("https://www.youtube.com/feeds/videos.xml?channel_id=",
                 channel_id)

entry.nodes <- rss_url %>%
    read_html() %>%
    html_nodes("entry")

vid = entry.nodes %>% xml_node("videoid") %>% html_text()
title = entry.nodes %>% html_node("title") %>% html_text()
link = entry.nodes %>% html_node("link") %>% html_attr("href")
published  = entry.nodes %>% html_node("published") %>% html_text() %>%
    ymd_hms(tz = "Asia/Taipei")
description = entry.nodes %>% html_node("group description") %>% html_text() %>% trimws()
views = entry.nodes %>% html_node("group community statistics") %>% html_attr("views")

video_rss.tb <- tibble(vid = vid, title = title, link = link,
             published = published, description = description, views = views)