Read <table> HTML tag with {rvest} using CSS selectors

rvest_read_tbl.R

# Read <table> HTML tag with {rvest} using CSS selectors
# ====================================================

# Load library
library(rvest)

# =======================
# Read the web page [accessed 08-Apr-2017]
# =======================
link <- "http://www.theplantlist.org/1.1/statistics/"
# NOTE: is ethical to store the page and not read it unnecessarily too many times, 
# overloading their server
link.scrap <- read_html(link)

# =======================
# Use the general "table" selector to read all tables,
# then select desired table
# =======================
# -----------------------
# Without piping:
# -----------------------
tbl.nodes <- html_nodes(x   = link.scrap, 
                        css ="table")
tbls.lst  <- html_table(tbl.nodes)
# The result is a list, 
# therefore, an individual table can be further accessed via indexing
# so, select only the first table
my.tbl    <- tbls.lst[[1]]
# also, drop unwanted first column
my.tbl    <- my.tbl[,-1]
# adjust column name
colnames(my.tbl)[3] <- "Total_prc"
my.tbl
##       Status   Total Total_prc
## 1   Accepted 350,699     33.0%
## 2    Synonym 470,624     44.2%
## 3   Unplaced     243      0.0%
## 4 Unassessed 242,469     22.8%

# Note that all data is read as character!
str(my.tbl)
## 'data.frame':	4 obs. of  3 variables:
##  $ Status   : chr  "Accepted" "Synonym" "Unplaced" "Unassessed"
##  $ Total    : chr  "350,699" "470,624" "243" "242,469"
##  $ Total_prc: chr  "33.0%" "44.2%" "0.0%" "22.8%"

# -----------------------
# With piping:
# -----------------------
my.tbl.2 <- 
    html_nodes(x   = link.scrap, 
               css ="table") %>%
    html_table() %>%
    .[[1]] %>% # select the first table
    .[,-1]     # drop unwanted first column
# adjust column name
colnames(my.tbl.2)[3] <- "Total_prc"
my.tbl.2

# =======================
# Read a specific table tag from the page
# using directly the table's selector
# =======================
my.tbl.3 <- 
    html_nodes(x   = link.scrap, 
               css ='#columns > section > div:nth-child(5) > table') %>%
    html_table() %>% 
    .[[1]] %>% # The indexing is to select the only element of the list
    .[,-1]     # drop unwanted first column
colnames(my.tbl.3)[3] <- "Total_prc"
my.tbl.3