R 中的网页抓取：解析 HTML 表格的问题

Question

I have been trying to scrape a table from a website so that I can reformat it in R. I have done this before for other websites, but am finding this to be particularly challenging. My code is below:

library(rvest)

URL <- "http://www.barttorvik.com/schedule.php"
uastring <- "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36"
page <- read_html(GET(URL, user_agent(uastring)))

tbls <- page %>%
  html_nodes("#tblData") %>% # name of the table on the website
  html_table(trim = FALSE) # This returns a data frame with the right columns but no data

If you run this, you will see that this returns an empty data frame (or a list of an empty data frame). I have been looking through other threads and have yet to find a fix.

I appreciate your feedback!

Answer 1

This table seems to have an addition row using colspan="6"

page %>%
  html_nodes("td") %>% tail(1)

{xml_nodeset (1)}
[1] <td colspan="6" style="background: #5b9bd5; color: #fff; text-transform: uppercase;\r\ntext-align:center; font-size:10px">MOV Mean absolute error: 7.57 | Totals MAE: 29.8 | \r\nScore bias: -29.8 |<span cl ...

I think this could somehow be solved with the unpivotr package

Otherwise you can try:

library(rvest)

URL <- "http://www.barttorvik.com/schedule.php"
uastring <- "Mozilla/5.0 (Windows NT 6.1) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/41.0.2228.0 Safari/537.36"
page <- read_html(GET(URL, user_agent(uastring)))

cols<- page %>%
  html_nodes("th") %>%
  html_text()

data <- page %>%
  html_nodes("td") %>%
  html_text()


finaldata <- data.frame(matrix(data[-126], ncol=5, byrow=TRUE)) # leavs out the colspan
names(finaldata) <- cols

finaldata

  Time (CT)                                              Matchup                            T-Rank Line TTQ      Result
1    6:00 PM                 45 North Carolina St. at 52 Virginia             Virginia -2.5, 58-55 (62%)  65            
2    6:00 PM                         55 Texas at 10 West Virginia        West Virginia -9.4, 67-58 (85%)  60            
3    8:00 PM                              58 Oklahoma at 5 Baylor              Baylor -12.8, 75-63 (89%)  59            
4    3:00 PM                    108 Charlotte at 186 Old Dominion            Charlotte -0.5, 57-56 (53%)  59            
5    6:00 PM                          146 Winthrop at 161 Radford              Radford -3.1, 74-71 (62%)  54            
6    7:30 PM              233 Texas Southern at 289 Grambling St.        Grambling St. -0.0, 76-75 (50%)  54            
7    3:00 PM                       241 LIU Brooklyn at 313 Wagner         LIU Brooklyn -0.9, 78-77 (53%)  49            
8    4:00 PM                215 Sacred Heart at 228 Robert Morris        Robert Morris -2.9, 74-71 (61%)  47            
9    6:30 PM             285 North Carolina A&T at 311 Morgan St.           Morgan St. -2.4, 72-69 (60%)  41            
10   6:00 PM                    259 UNC Asheville at 334 Longwood        UNC Asheville -2.8, 75-72 (61%)  40            
11   7:30 PM              179 Prairie View A&M at 322 Jackson St.     Prairie View A&M -5.5, 70-64 (72%)  39            
12   3:00 PM        301 North Carolina Central at 288 Florida A&M          Florida A&M -3.7, 65-61 (66%)  35            
13   6:00 PM                     234 Campbell at 331 Presbyterian             Campbell -3.1, 65-62 (64%)  34            
14   6:00 PM                          263 Bucknell at 156 Colgate             Colgate -10.6, 77-66 (85%)  34            
15   7:00 PM                           251 Rice at 60 North Texas         North Texas -16.2, 77-60 (94%)  32            
16   3:00 PM                  271 Merrimack at 188 St. Francis PA       St. Francis PA -8.2, 68-60 (82%)  30            
17   7:30 PM            315 Alcorn St. at 347 Arkansas Pine Bluff           Alcorn St. -3.2, 66-62 (64%)  28            
18   6:00 PM           317 St. Francis NY at 275 Mount St. Mary's     Mount St. Mary's -5.4, 67-61 (73%)  28            
19   9:05 PM                    310 Weber St. at 184 Portland St.        Portland St. -12.2, 78-66 (87%)  26            
20   6:00 PM                      327 Hampton at 248 Gardner Webb        Gardner Webb -10.2, 81-71 (82%)  24            
21  11:00 AM                                64 Yale at 348 Howard                Yale -21.6, 78-56 (98%)  19 Yale, 89-75
22   4:00 PM           278 Southern at 351 Mississippi Valley St.            Southern -10.5, 80-69 (84%)  15            
23   5:00 PM                    344 High Point at 306 USC Upstate         USC Upstate -10.0, 74-64 (84%)  15            
24   2:30 PM   350 Central Connecticut at 320 Fairleigh Dickinson Fairleigh Dickinson -14.6, 80-66 (91%)   5            
25   6:30 PM 352 Maryland Eastern Shore at 323 South Carolina St.  South Carolina St. -15.8, 75-60 (94%)   0  

Answer 2

For whatever reason your page ( http://www.barttorvik.com/schedule.php ) lacks opening <tr> elements for the table body. They are present in table header - <thead> part but not in <tbody> . You can easily verify this by opening page source (Ctrl+U) and searching for tr> - you will find closing elements </tr> in the table, but not <tr> .

If you correct this by adding missing elements all works. Browsers are programmed to cope with bad html (they render), but rvest does not know what to do with this, therefore it only displays header row. You could write code to insert <tr> before every <td style='text-align:left;white-space:nowrap' id="mobileout"> or maybe you could tell page authors to correct their code generator?

> mypage <- read_html("~/tmp/test.html")
# test.html is file where I made the necessary replacements
> mypage%>% html_nodes('table') %>% html_table()
[[1]]
   Time (CT)                                              Matchup                            T-Rank Line TTQ Result
1    6:00 PM                 45 North Carolina St. at 51 Virginia             Virginia -2.5, 58-55 (62%)  65     NA
2    6:00 PM                         55 Texas at 10 West Virginia        West Virginia -9.4, 67-58 (85%)  60     NA
3    3:00 PM                    109 Charlotte at 186 Old Dominion            Charlotte -0.5, 57-56 (53%)  59     NA
4    6:00 PM                          145 Winthrop at 161 Radford              Radford -3.0, 74-71 (62%)  54     NA
5    7:30 PM              233 Texas Southern at 288 Grambling St.        Grambling St. -0.0, 76-75 (50%)  54     NA
6    3:00 PM                       240 LIU Brooklyn at 312 Wagner         LIU Brooklyn -0.9, 78-77 (54%)  49     NA
7    4:00 PM                215 Sacred Heart at 230 Robert Morris        Robert Morris -2.9, 74-71 (61%)  47     NA
8    6:30 PM             284 North Carolina A&T at 313 Morgan St.           Morgan St. -2.3, 72-69 (59%)  41     NA
9    6:00 PM                    259 UNC Asheville at 334 Longwood        UNC Asheville -2.8, 75-72 (61%)  40     NA
10   7:30 PM              179 Prairie View A&M at 323 Jackson St.     Prairie View A&M -5.5, 70-64 (72%)  39     NA
11   3:00 PM        302 North Carolina Central at 289 Florida A&M          Florida A&M -3.7, 65-61 (66%)  35     NA
12   6:00 PM                     234 Campbell at 331 Presbyterian             Campbell -3.1, 65-62 (64%)  34     NA
13   6:00 PM                          263 Bucknell at 156 Colgate             Colgate -10.5, 77-66 (84%)  34     NA
14   7:00 PM                           251 Rice at 61 North Texas         North Texas -16.2, 77-60 (94%)  32     NA
15   3:00 PM                  271 Merrimack at 188 St. Francis PA       St. Francis PA -8.2, 68-60 (82%)  30     NA
16   7:30 PM            315 Alcorn St. at 347 Arkansas Pine Bluff           Alcorn St. -3.2, 66-62 (64%)  28     NA
17   6:00 PM           317 St. Francis NY at 278 Mount St. Mary's     Mount St. Mary's -5.4, 67-61 (72%)  28     NA
18   9:05 PM                    310 Weber St. at 184 Portland St.        Portland St. -12.1, 78-66 (87%)  26     NA
19   6:00 PM                      327 Hampton at 249 Gardner Webb        Gardner Webb -10.3, 82-71 (82%)  24     NA
20  11:00 AM                                60 Yale at 348 Howard                Yale -21.6, 78-56 (98%)  18     NA
21   4:00 PM           277 Southern at 351 Mississippi Valley St.            Southern -10.5, 80-69 (83%)  15     NA
22   5:00 PM                    344 High Point at 306 USC Upstate         USC Upstate -10.0, 74-64 (84%)  15     NA
23   2:30 PM   350 Central Connecticut at 320 Fairleigh Dickinson Fairleigh Dickinson -14.6, 80-66 (91%)   5     NA
24   6:30 PM 352 Maryland Eastern Shore at 324 South Carolina St.  South Carolina St. -15.8, 76-60 (94%)   0     NA