[問題] Error in UseMethod("xml_find_all")

看板R_Language作者k5171 (Jess)時間8年前 (2017/02/04 19:21)推噓2(2推 0噓 39→)

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各位版大好，首次使用Ｒ爬蟲，嘗試其他網頁的爬蟲都有成功，唯獨此篇的網頁一直爬不下來，嘗試多日真的快想破頭，懇請版上大大能幫忙！ [問題類型]: 程式諮詢(我想用R 做某件事情，但是我不知道要怎麼用R 寫出來) [軟體熟悉度]: 新手(沒寫過程式，R 是我的第一次) [問題敘述]: library(httr) library(rvest) etf_url <- "http://etfdb.com/etfdb-category/high-yield-bonds/" 首先想爬這個表格就嘗試了幾個方法： # Definitive List Of High Yield Bonds ETFs (I) hyetf <- read_html(etf_url) %>% html_nodes(xpath = '//*[@id="etfs"]') %>% html_table() ==> hyetf 顯示為 list() (II) etf <- content(GET(etf_url), as = "text", encoding = "UTF-8") hyetf <- etf %>% html_nodes(xpath = '//*[@id="etfs"]') %>% html_table() hyetf ==> Error in UseMethod("xml_find_all") : 沒有適用的方法可將 'xml_find_all' 套用到 "character" 類別的物件; hyetf 同樣顯示為 list() (III) 想說試試看用爬 <table> tag 的方式，結果卻發現找不到 <table> tag 的 list: hyetftable <- read_html(etf_url) %>% hyetftable <- read_html(etf_url) %>% html_nodes("table") ==> {xml_nodeset (0)} 於是不死心決定爬個入門版的最上方大標題試試，結果還是失敗了 # 網頁頂層大標 High Yield Bond ETFs (I) hyetf <- etf %>% html_nodes(".mm-heading-no-top-margin") %>% html_nodes("h1") %>% html_text() ==> Error in UseMethod("xml_find_all") : 沒有適用的方法可將 'xml_find_all' 套用到 "character" 類別的物件; hyetf 顯示為 character(0) (II) hyetf <- read_html(etf_url) %>% html_nodes(".mm-heading-no-top-margin") %>% html_nodes("h1") %>% html_text() ==> hyetf 仍顯示為 character(0) 嘗試了好幾週，真的不確定是哪裡缺少什麼，懇請版上大大賜教，感激！ [環境敘述]: > sessionInfo() R version 3.3.1 (2016-06-21) Platform: x86_64-apple-darwin13.4.0 (64-bit) Running under: OS X 10.11.6 (El Capitan) locale: [1] zh_TW.UTF-8/zh_TW.UTF-8/zh_TW.UTF-8/C/zh_TW.UTF-8/zh_TW.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets [6] methods base other attached packages: [1] httr_1.2.1 Rwordseg_0.2-1 ggplot2_2.2.0 [4] jiebaR_0.9.1 jiebaRD_0.1 tmcn_0.1-4 [7] tm_0.6-2 NLP_0.1-9 rJava_0.9-8 [10] rvest_0.3.2 xml2_1.0.0 loaded via a namespace (and not attached): loaded via a namespace (and not attached): [1] Rcpp_0.12.7 magrittr_1.5 [3] munsell_0.4.3 colorspace_1.2-6 [5] R6_2.1.3 stringr_1.1.0 [7] plyr_1.8.4 tools_3.3.1 [9] parallel_3.3.1 grid_3.3.1 [11] gtable_0.2.0 selectr_0.3-0 [13] lazyeval_0.2.0 assertthat_0.1 [15] tibble_1.2 curl_2.1 [17] rsconnect_0.4.3 slam_0.1-40 [19] stringi_1.1.1 scales_0.4.1 [21] XML_3.98-1.5 -- ※ 發信站: 批踢踢實業坊(ptt.cc), 來自: 49.214.198.211 ※ 文章網址: https://www.ptt.cc/bbs/R_Language/M.1486207270.A.8F8.html

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