使用RVest进行搜寻时，预期的html_node不出现

Question

The ITTO website produces a table of timber products and flows directly under the search form once the query is submitted (on the same page). Using information I obtained from Chrome's SelectorGadget I'm expecting the table to appear as the css element "td". Using rvest to scrape information on Albania for 2014...

library(rvest)

session <- html_session("http://www.itto.int/annual_review_output/?mode=searchdata")
form <- html_form(session)[[2]]
form <- set_values(form, "countries[]" = "8", "products[]" = "1" ,"flows[]" = "1", "years[]" = "2014")
query <- submit_form(session, form, submit = NULL)
page <- read_html(query) %>% html_nodes("td")
page 

Which results in the table "td" being absent:

{xml_nodeset (0)}

Examining other elements of the page with html_nodes() suggests that submit_form() performed otherwise as expected.

So my question is where is the expected table?

Answer 1

It might be easier (in the long run) to scrape the select box options and just feed the POST call directly:

library(httr)
library(rvest)

res <- POST(url = "http://www.itto.int/annual_review_output/?mode=searchdata",
            body = list(`countries[]` = "76", 
                        `products[]` = "1", `flows[]` = "1", 
                        `years[]` = "2014"), 
            encode = "form")

pg <- content(res, as="parsed")
html_nodes(pg, "td")

## {xml_nodeset (7)}
## [1] <td>Brazil</td>
## [2] <td>Ind. roundwood</td>
## [3] <td>Exports Quantity</td>
## [4] <td>1000 m3</td>
## [5] <td>2014</td>
## [6] <td style="text-align:right;">204.59</td>
## [7] <td>I</td>