部署时出现闪亮应用程序错误，在本地工作（rvest-->；html_节点问题）

我有一个闪亮的应用程序，可以从亚特兰大警察局的网站下载一个zip文件，然后将其解压成临时文件。该应用程序在本地运行良好，但当我将其部署到shinyapps.io时，我得到一个错误：

找不到函数“xpath\u combinedselector”

我将其锁定为对R包“rvest”的调用，即函数“html\u nodes”（它使用包“selector”将CSS选择器转换为XML）。我认为这与光鲜端的版本控制有关，但我一直在思考如何修复它

作为参考，犯罪数据下载网站是：我正在使用底部的zip文件（每周使用不同的url更新）：“2009-20yy犯罪数据文件原始数据（mm/dd/yyyy）”

代码生成错误：

# load libraries (some of these are used later on in the app, but 
# included here in case they might be the cause)
library(shiny); library(lubridate); library(ggplot2)
library(ggmap); library(RgoogleMaps); library(readr)
library(rvest); library(dplyr)

# Set up temp file to download zip file to
temp <- tempfile()

# Download zip file from location on APD website, to above temp file
download.file(
   read_html("http://www.atlantapd.org/crimedatadownloads.aspx") %>% 
      # THE NEXT LINE IS THE PROBLEM CHILD
      html_nodes("tr:nth-child(15) a") %>% 
      html_attr("href") %>% 
      paste0("http://www.atlantapd.org/", .),
   destfile = temp)

#加载库（有些库稍后会在应用程序中使用，但是
#包括在此处，以防它们可能是原因）
图书馆（闪亮）；图书馆（lubridate）；图书馆（GG2）
图书馆（ggmap）；图书馆（RgoogleMaps）；图书馆（readr）
图书馆（rvest）；图书馆（dplyr）
#设置要将zip文件下载到的临时文件
温度%
#下一行是有问题的孩子
html_节点（“tr:n子（15）a”）%>%
html_attr（“href”）%%>%
粘贴0（“http://www.atlantapd.org/", .),
destfile=temp）

应用程序错误日志：

2016-05-21T19:47:43.603137+00:00 shinyapps[103450]: Warning: Error in do.call: could not find function "xpath_combinedselector"
2016-05-21T19:47:43.610211+00:00 shinyapps[103450]: Stack trace (innermost first):
2016-05-21T19:47:43.610213+00:00 shinyapps[103450]:     76: do.call
2016-05-21T19:47:43.610214+00:00 shinyapps[103450]:     75: .self$xpath
2016-05-21T19:47:43.610216+00:00 shinyapps[103450]:     74: selector_to_xpath
2016-05-21T19:47:43.610217+00:00 shinyapps[103450]:     73: FUN
2016-05-21T19:47:43.610218+00:00 shinyapps[103450]:     72: lapply
2016-05-21T19:47:43.610221+00:00 shinyapps[103450]:     69: <Anonymous>
2016-05-21T19:47:43.610222+00:00 shinyapps[103450]:     68: mapply
2016-05-21T19:47:43.610223+00:00 shinyapps[103450]:     67: Map
2016-05-21T19:47:43.610224+00:00 shinyapps[103450]:     66: selectr::css_to_xpath
2016-05-21T19:47:43.610225+00:00 shinyapps[103450]:     65: make_selector
2016-05-21T19:47:43.610226+00:00 shinyapps[103450]:     64: node_find_all
2016-05-21T19:47:43.610227+00:00 shinyapps[103450]:     63: xml_find_all.xml_node
2016-05-21T19:47:43.610220+00:00 shinyapps[103450]:     70: tran$css_to_xpath
2016-05-21T19:47:43.610230+00:00 shinyapps[103450]:     60: html_nodes
2016-05-21T19:47:43.610219+00:00 shinyapps[103450]:     71: sapply
2016-05-21T19:47:43.610232+00:00 shinyapps[103450]:     58: withVisible
2016-05-21T19:47:43.610233+00:00 shinyapps[103450]:     57: freduce
2016-05-21T19:47:43.610234+00:00 shinyapps[103450]:     56: _fseq
2016-05-21T19:47:43.610235+00:00 shinyapps[103450]:     55: eval
2016-05-21T19:47:43.610236+00:00 shinyapps[103450]:     54: eval
2016-05-21T19:47:43.610237+00:00 shinyapps[103450]:     53: withVisible
2016-05-21T19:47:43.610238+00:00 shinyapps[103450]:     52: %>%
2016-05-21T19:47:43.610231+00:00 shinyapps[103450]:     59: function_list[[k]]
2016-05-21T19:47:43.610229+00:00 shinyapps[103450]:     61: html_nodes.default
2016-05-21T19:47:43.610228+00:00 shinyapps[103450]:     62: xml2::xml_find_all
2016-05-21T19:47:43.610242+00:00 shinyapps[103450]:      9: tryCatchList
2016-05-21T19:47:43.610243+00:00 shinyapps[103450]:      8: tryCatch
2016-05-21T19:47:43.610244+00:00 shinyapps[103450]:      7: connect$retry
2016-05-21T19:47:43.610245+00:00 shinyapps[103450]:      6: eval
2016-05-21T19:47:43.610246+00:00 shinyapps[103450]:      5: eval
2016-05-21T19:47:43.610238+00:00 shinyapps[103450]:     13: runApp
2016-05-21T19:47:43.610247+00:00 shinyapps[103450]:      3: eval
2016-05-21T19:47:43.610239+00:00 shinyapps[103450]:     12: fn
2016-05-21T19:47:43.610240+00:00 shinyapps[103450]:     11: doTryCatch
2016-05-21T19:47:43.610241+00:00 shinyapps[103450]:     10: tryCatchOne
2016-05-21T19:47:43.610415+00:00 shinyapps[103450]: Error in do.call(method, list(parsed_selector)) : 
2016-05-21T19:47:43.610248+00:00 shinyapps[103450]:      2: eval.parent
2016-05-21T19:47:43.610247+00:00 shinyapps[103450]:      4: eval
2016-05-21T19:47:43.610249+00:00 shinyapps[103450]:      1: local

2016-05-21T19:47:43.603137+00:00 shinyapps[103450]：警告：do.call中出错：找不到函数“xpath\u combinedselector”
2016-05-21T19:47:43.610211+00:00 shinyapps[103450]：堆栈跟踪（最里面的第一个）：
2016-05-21T19:47:43.610213+00:00 shinyapps[103450]：76:do.call
2016-05-21T19:47:43.610214+00:00Shinyapps[103450]：75:.self$xpath
2016-05-21T19:47:43.610216+00:00 shinyapps[103450]：74:选择器
2016-05-21T19:47:43.610217+00:00 shinyapps[103450]：73:乐趣
2016-05-21T19:47:43.610218+00:00 shinyapps[103450]：72:lappy
2016-05-21T19:47:43.610221+00:00 shinyapps[103450]：69:
2016-05-21T19:47:43.610222+00:00Shinyapps[103450]：68:mapply
2016-05-21T19:47:43.610223+00:00 shinyapps[103450]：67:地图
2016-05-21T19:47:43.610224+00:00Shinyapps[103450]：66:selectr:：css_to_xpath
2016-05-21T19:47:43.610225+00:00 shinyapps[103450]：65:make_选择器
2016-05-21T19:47:43.610226+00:00 shinyapps[103450]：64:node_find_all
2016-05-21T19:47:43.610227+00:00 shinyapps[103450]：63:xml\u find\u all.xml\u节点
2016-05-21T19:47:43.610220+00:00Shinyapps[103450]：70:tran$css_to_xpath
2016-05-21T19:47:43.610230+00:00Shinyapps[103450]：60:html_节点
2016-05-21T19:47:43.610219+00:00 shinyapps[103450]：71:sapply
2016-05-21T19:47:43.610232+00:00 shinyapps[103450]：58:可见
2016-05-21T19:47:43.610233+00:00 shinyapps[103450]：57:freduce
2016-05-21T19:47:43.610234+00:00 shinyapps[103450]：56:
2016-05-21T19:47:43.610235+00:00 shinyapps[103450]：55:eval
2016-05-21T19:47:43.610236+00:00 shinyapps[103450]：54:eval
2016-05-21T19:47:43.610237+00:00 shinyapps[103450]：53:withVisible
2016-05-21T19:47:43.610238+00:00Shinyapps[103450]：52:%>%
2016-05-21T19:47:43.610231+00:00 shinyapps[103450]：59:功能列表[k]]
2016-05-21T19:47:43.610229+00:00 shinyapps[103450]：61:html_nodes.default
2016-05-21T19:47:43.610228+00:00 shinyapps[103450]：62:xml2:：xml_find_all
2016-05-21T19:47:43.610242+00:00Shinyapps[103450]：9:tryCatchList
2016-05-21T19:47:43.610243+00:00Shinyapps[103450]：8:tryCatch
2016-05-21T19:47:43.610244+00:00Shinyapps[103450]：7:connect$retry
2016-05-21T19:47:43.610245+00:00 shinyapps[103450]：6:eval
2016-05-21T19:47:43.610246+00:00 shinyapps[103450]：5:eval
2016-05-21T19:47:43.610238+00:00 shinyapps[103450]：13:runApp
2016-05-21T19:47:43.610247+00:00 shinyapps[103450]：3:eval
2016-05-21T19:47:43.610239+00:00 shinyapps[103450]：12:fn
2016-05-21T19:47:43.610240+00:00 shinyapps[103450]：11:doTryCatch
2016-05-21T19:47:43.610241+00:00 shinyapps[103450]：10:tryCatchOne
2016-05-21T19:47:43.610415+00:00Shinyapps[103450]：do.call（方法、列表（已解析的_选择器））中出错：
2016-05-21T19:47:43.610248+00:00 shinyapps[103450]：2:eval.parent
2016-05-21T19:47:43.610247+00:00 shinyapps[103450]：4:eval
2016-05-21T19:47:43.610249+00:00 shinyapps[103450]：1:本地

问题在于在为

html\u节点

函数。此函数只有一个参数，css或xpath

如果不指定参数类型（在本例中是css选择器），则该参数将视为xpath（这就是为什么

错误：找不到函数“xpath\u combinedselector”

）。因此，为了确保Shining服务器在部署应用程序时能够识别您提供的参数类型，您应该指定

html\u节点

参数，如下所示：

 html_nodes(css="tr:nth-child(15) a")