在R中按组计算字符串模式

Question

我正在尝试使用 R 获取数据框中某个字符串的分组计数，但到目前为止还没有找到解决方案。以下是我尝试使用的一些示例数据和代码，以便您了解我要完成的工作，以及下面的进一步说明：

simpson <- structure(list(season = c(1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 1L, 
1L, 1L, 1L, 1L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 
2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 2L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 3L, 
3L, 3L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 
4L, 4L, 4L, 4L, 4L, 4L, 4L, 4L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 
5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L, 5L), episode_title = c("Simpsons Roasting on an Open Fire", 
"Bart the Genius", "Homer's Odyssey", "There's No Disgrace Like Home", 
"Bart the General", "Moaning Lisa", "The Call of the Simpsons", 
"The Telltale Head", "Life on the Fast Lane", "Homer's Night Out", 
"The Crepes of Wrath", "Krusty Gets Busted", "Some Enchanted Evening", 
"Bart Gets an \"F\"", "Simpson and Delilah", "Treehouse of Horror", 
"Two Cars in Every Garage and Three Eyes on Every Fish", "Dancin' Homer", 
"Dead Putting Society", "Bart vs. Thanksgiving", "Bart the Daredevil", 
"Itchy & Scratchy & Marge", "Bart Gets Hit by a Car", "One Fish, Two Fish, Blowfish, Blue Fish", 
"The Way We Was", "Homer vs. Lisa and the 8th Commandment", "Principal Charming", 
"Oh Brother, Where Art Thou?", "Bart's Dog Gets an \"F\"", "Old Money", 
"Brush with Greatness", "Lisa's Substitute", "The War of the Simpsons", 
"Three Men and a Comic Book", "Blood Feud", "Stark Raving Dad", 
"Mr. Lisa Goes to Washington", "When Flanders Failed", "Bart the Murderer", 
"Homer Defined", "Like Father, Like Clown", "Treehouse of Horror II", 
"Lisa's Pony", "Saturdays of Thunder", "Flaming Moe's", "Burns Verkaufen der Kraftwerk", 
"I Married Marge", "Radio Bart", "Lisa the Greek", "Homer Alone", 
"Bart the Lover", "Homer at the Bat", "Separate Vocations", "Dog of Death", 
"Colonel Homer", "Black Widower", "The Otto Show", "Bart's Friend Falls in Love", 
"Brother, Can You Spare Two Dimes?", "Kamp Krusty", "A Streetcar Named Marge", 
"Homer the Heretic", "Lisa the Beauty Queen", "Treehouse of Horror III", 
"Itchy & Scratchy: The Movie", "Marge Gets a Job", "New Kid on the Block", 
"Mr. Plow", "Lisa's First Word", "Homer's Triple Bypass", "Marge vs. the Monorail", 
"Selma's Choice", "Brother from the Same Planet", "I Love Lisa", 
"Duffless", "Last Exit to Springfield", "So It's Come to This: A Simpsons Clip Show", 
"The Front", "Whacking Day", "Marge in Chains", "Krusty Gets Kancelled", 
"Homer's Barbershop Quartet", "Cape Feare", "Homer Goes to College", 
"Rosebud", "Treehouse of Horror IV", "Marge on the Lam", "Bart's Inner Child", 
"Boy-Scoutz 'n the Hood", "The Last Temptation of Homer", "$pringfield (or, How I Learned to Stop Worrying and Love Legalized Gambling)", 
"Homer the Vigilante", "Bart Gets Famous", "Homer and Apu", "Lisa vs. Malibu Stacy", 
"Deep Space Homer", "Homer Loves Flanders", "Bart Gets an Elephant", 
"Burns' Heir", "Sweet Seymour Skinner's Baadasssss Song"), imdb_votes = c(3734L, 
1973L, 1709L, 1701L, 1732L, 1674L, 1638L, 1580L, 1578L, 1511L, 
1539L, 1716L, 1567L, 1638L, 1588L, 1786L, 1457L, 1381L, 1366L, 
1324L, 1522L, 1402L, 1340L, 1687L, 1392L, 1329L, 1241L, 1413L, 
1264L, 1243L, 1257L, 1684L, 1246L, 1379L, 1223L, 1798L, 1274L, 
1302L, 1446L, 1452L, 1262L, 1369L, 1243L, 1194L, 1618L, 1291L, 
1213L, 1365L, 1179L, 1176L, 1272L, 1637L, 1201L, 1165L, 1233L, 
1233L, 1176L, 1160L, 1227L, 1414L, 1339L, 1747L, 1194L, 1394L, 
1293L, 1163L, 1240L, 1595L, 1350L, 1445L, 2028L, 1153L, 1176L, 
1268L, 1209L, 1827L, 1105L, 1122L, 1234L, 1080L, 1269L, 1416L, 
2010L, 1476L, 1479L, 1437L, 1132L, 1085L, 1270L, 1308L, 1274L, 
1202L, 1123L, 1171L, 1187L, 1505L, 1191L, 1116L, 1143L, 1118L
), us_viewers_in_millions = c(26.7, 24.5, 27.5, 20.2, 27.1, 27.4, 
27.6, 28, 33.5, 30.3, 31.2, 30.4, 27.1, 33.6, 29.9, 27.4, 26.1, 
26.1, 25.4, 25.9, 26.2, 22.2, 24.8, 24.2, 26.8, 26.2, 23.9, 26.8, 
23.9, 21.2, 20.6, 17.7, 19.7, 21, 17.3, 22.9, 20.2, 22.8, 20.8, 
20.6, 20.2, 20, 23, 24.7, 23.9, 21.1, 21.9, 24.2, 23.2, 23.7, 
20.5, 24.6, 23.7, 23.4, 25.5, 17.3, 17.5, 19.5, 17.2, 21.8, 18.3, 
19.3, 19, 25.1, 20.1, 22.9, 23.1, 24, 28.6, 23.6, 23, 24.5, 23.8, 
25.2, 25.7, 22.4, 25.5, 20.1, 20, 17.3, 19.4, 19.9, 20, 18.1, 
19.5, 24, 21.7, 18.7, 20.1, 20.6, 17.9, 20.1, 20, 21.8, 20.5, 
18.2, 18, 17, 14.7, 19.7)), .Names = c("season", "episode_title", 
"imdb_votes", "us_viewers_in_millions"), row.names = c(NA, -100L
), class = c("tbl_df", "tbl", "data.frame"))

char_counts <- simpson %>%
  group_by(season) %>%
  str_count(episode_title, "Homer")

所以我首先按季节对数据进行分组，然后我试图计算在给定季节的任何剧集的标题中出现“荷马”一词的总次数。

任何关于我哪里出错的建议将不胜感激。

最好， 柯蒂斯

Answer 1

要向每一行添加一个新变量，您需要使用mutate 函数。 group_by 不需要，除非您想按组汇总：

simpson %>%
    mutate(homer_count = str_count(episode_title, 'Homer'))

# A tibble: 100 x 5
   season episode_title                     imdb_votes us_viewers_in_millions homer_count
    <int> <chr>                                  <int>                  <dbl>       <int>
 1      1 Simpsons Roasting on an Open Fire       3734                   26.7           0
 2      1 Bart the Genius                         1973                   24.5           0
 3      1 Homer's Odyssey                         1709                   27.5           1
 4      1 There's No Disgrace Like Home           1701                   20.2           0
 5      1 Bart the General                        1732                   27.1           0
 6      1 Moaning Lisa                            1674                   27.4           0
 7      1 The Call of the Simpsons                1638                   27.6           0
 8      1 The Telltale Head                       1580                   28             0
 9      1 Life on the Fast Lane                   1578                   33.5           0
10      1 Homer's Night Out                       1511                   30.3           1
# ... with 90 more rows

如果您想计算每个季节使用Homer 的次数，您可以先group_by 然后使用summarize 生成一个新变量，每组一行：

simpson %>%
    group_by(season) %>%
    summarize(homer_count = sum(str_count(episode_title, 'Homer')))

# A tibble: 5 x 2
  season homer_count
   <int>       <int>
1      1           2
2      2           2
3      3           4
4      4           2
5      5           7

Answer 2

library(dplyr)

simpson %>%
  mutate(counts = str_count(episode_title, "Homer")) %>%  # count matches for each row (vectorised function)
  group_by(season) %>%                                    # for each season
  summarise(sum_counts = sum(counts))                     # sum counts

# # A tibble: 5 x 2
#   season sum_counts
#    <int>      <int>
# 1      1          2
# 2      2          2
# 3      3          4
# 4      4          2
# 5      5          7