Loops RSelenium：在Dropbox中的所有值上循环

我试图通过以下链接为每个国家与所有与艾滋病毒/艾滋病相关的非政府组织拼凑出一张表格：

我可以导航到url并选择“HIV/AIDS”单选按钮。但是现在我还需要提取Dropbox'region'和'country'的所有值，这样我就可以在循环中使用它们来顺序地为每个国家创建表。如何收集两个Dropbox的值？到目前为止，我的代码如下：

#load library
library(RSelenium)

#Specify remote driver
remDr <- remoteDriver(browserName='firefox')

#Initialise session 
remDr$open()

#navigate to advanced search page

url <- "https://www.unodc.org/ngo/showExtendedSearch.do"
remDr$navigate(url)

#Click 'HIV/AIDS' filter
webElem <- remDr$findElement(using = 'css', 
                         value = '#applicationArea > form > table > tbody > tr > td > table:nth-child(7) > tbody > tr:nth-child(2) > td > table > tbody > tr > td:nth-child(2) > table > tbody > tr:nth-child(3) > td:nth-child(4) > input[type="checkbox"]')

webElem$clickElement()

#加载库
图书馆（资源库）
#指定远程驱动程序
remDr使用firebug或开发者工具确定下拉菜单元素的xpath，然后使用
getElementText
检索值：

 region_element <- remDr$findElement('xpath', '//*[@id="applicationArea"]/form/table/tbody/tr/td/table[2]/tbody/tr[2]/td/table/tbody/tr[1]/td[2]/select')
regions <- strsplit(region_element$getElementText()[[1]], "\n")

country_element <- remDr$findElement('xpath', '//*[@id="applicationArea"]/form/table/tbody/tr/td/table[2]/tbody/tr[2]/td/table/tbody/tr[2]/td[2]/select')
countries <- strsplit(country_element$getElementText()[[1]], "\n")

R> print(regions[[1]])
 [1] "Middle East and Northern Africa"   "Eastern Africa"                   
 [3] "Western Africa"                    "Central and Southern Africa"      
 [5] "Northern America"                  "Central America and the Caribbean"
 [7] "Latin America"                     "Central and Western Asia"         
 [9] "Southern and Eastern Asia"         "Europe"                           
[11] "Oceania"                          
R> print(head(countries[[1]]))
[1] "Afghanistan"    "Albania"        "Algeria"        "American Samoa" "Andorra"       
[6] "Angola"  

region\u元素