我正在练习抓取和数据清理，并且有一个我从维基百科上抓取的表。我试图改变表，以创建一个列，从现有的列中清除逗号返回的数字。我得到的是一列NAs
这是我的输出:
> library(dplyr)
> library(rvest)
>
> pg <- read_html("https://en.wikipedia.org/wiki/Rugby_World_Cup")
> rugby <- pg %>% html_table(., fill = T)
>
> rugby_table <- rugby[[3]]
>
> rugby_table
# A tibble: 9 x 8
Year `Host(s)` `Total attendance` Matches `Avg attendance` `% change in avg att.` `Stadium capacity` `Attendance as % o~
<int> <chr> <chr> <chr> <chr> <chr> <chr> <chr>
1 1987 Australia New Zealand 604,500 32 20,156 — 1,006,350 60%
2 1991 England France Ireland Scotland Wales 1,007,760 32 31,493 +56% 1,212,800 79%
3 1995 South Africa 1,100,000 32 34,375 +9% 1,423,850 77%
4 1999 Wales 1,750,000 41 42,683 +24% 2,104,500 83%
5 2003 Australia 1,837,547 48 38,282 –10% 2,208,529 83%
6 2007 France 2,263,223 48 47,150 +23% 2,470,660 92%
7 2011 New Zealand 1,477,294 48 30,777 –35% 1,732,000 85%
8 2015 England 2,477,805 48 51,621 +68% 2,600,741 95%
9 2019 Japan 1,698,528 45† 37,745 –27% 1,811,866 90%
>
> rugby_table2 <- rugby %>%
+ .[[3]] %>%
+ tbl_df %>%
+ mutate(Attendance=as.numeric(gsub("[^0-9.-]+","",'Total attendance')))
>
> rugby_table2
# A tibble: 9 x 9
Year `Host(s)` `Total attendance` Matches `Avg attendance` `% change in avg~ `Stadium capaci~ `Attendance as~ Attendance
<int> <chr> <chr> <chr> <chr> <chr> <chr> <chr> <dbl>
1 1987 Australia New Zealand 604,500 32 20,156 — 1,006,350 60% NA
2 1991 England France Ireland Scotland Wales 1,007,760 32 31,493 +56% 1,212,800 79% NA
3 1995 South Africa 1,100,000 32 34,375 +9% 1,423,850 77% NA
4 1999 Wales 1,750,000 41 42,683 +24% 2,104,500 83% NA
5 2003 Australia 1,837,547 48 38,282 –10% 2,208,529 83% NA
6 2007 France 2,263,223 48 47,150 +23% 2,470,660 92% NA
7 2011 New Zealand 1,477,294 48 30,777 –35% 1,732,000 85% NA
8 2015 England 2,477,805 48 51,621 +68% 2,600,741 95% NA
9 2019 Japan 1,698,528 45† 37,745 –27% 1,811,866 90% NA
任何想法?
这里的困难是gsub将'Total attendance'解释为字符串，而不是列名。我的自然反应是使用反引号而不是单引号，但随后我得到一个消息，这个对象无法找到。我不确定这里的问题是什么，但你可以使用across
rugby_table2 <- rugby_table %>%
mutate(Attendance = across(contains("Total"),
function(x) as.numeric(gsub(",", "", x))),
Attendance = Attendance[[1]])
rugby_table2$Attendance
#> [1] 604500 1007760 1100000 1750000 1837547 2263223 1477294 2477805 1698528
编辑
Ronak Shah已经发现了这个问题，那就是在网页的名字中有一个看不见的字符，这意味着该栏目无法被识别。所以另一个解决方案是:
names(rugby_table)[3] <- "Total attendance"
rugby_table2 <- rugby_table %>%
mutate(Attendance = as.numeric(gsub(",", "", `Total attendance`)))
rugby_table2$Attendance
#> [1] 604500 1007760 1100000 1750000 1837547 2263223 1477294 2477805
gsub函数是对所提供模式的所有匹配进行替换。如果要用gsub删除所有的逗号，正确的语法应该是
rugby_table2 <- rugby %>%
.[[3]] %>%
tbl_df %>%
mutate(Attendance = as.numeric(gsub(",", "", 'Total attendance')))
编辑:
rugby_table <- structure(list(Year = c(1987L, 1991L, 1995L, 1999L, 2003L, 2007L,
2011L, 2015L, 2019L), `Host(s)` = c("AustraliaNewZealand", "EnglandFranceIrelandScotlandWales",
"SouthAfrica", "Wales", "Australia", "France", "NewZealand",
"England", "Japan"), `Total attendance` = c("604,500", "1,007,760",
"1,100,000", "1,750,000", "1,837,547", "2,263,223", "1,477,294",
"2,477,805", "1,698,528"), Matches = c("32", "32", "32", "41",
"48", "48", "48", "48", "45+"), `Avg attendance` = c("20,156",
"31,493", "34,375", "42,683", "38,282", "47,150", "30,777", "51,621",
"37,745"), `% change in avg att` = c("—", "56%", "9%", "24%",
"–10%", "23%", "–35%", "68%", "–27%"), `Stadium capacity` = c("1,006,350",
"1,212,800", "1,423,850", "2,104,500", "2,208,529", "2,470,660",
"1,732,000", "2,600,741", "1,811,866"), `Attendance as % o~` = c("60%",
"79%", "77%", "83%", "83%", "92%", "85%", "95%", "90%")), row.names = c(NA,
-9L), class = c("tbl_df", "tbl", "data.frame"))
library(dplyr)
rugby_table %>%
mutate(Attendance = as.numeric(gsub(",", "", `Total attendance`))) %>%
select(Attendance)
#> # A tibble: 9 x 1
#> Attendance
#> <dbl>
#> 1 604500
#> 2 1007760
#> 3 1100000
#> 4 1750000
#> 5 1837547
#> 6 2263223
#> 7 1477294
#> 8 2477805
#> 9 1698528