Question

这是我的数据框，仅由1个观察值组成。这是一个很长的字符串，可以识别4个不同的部分：

example <- "4.6             (19 ratings)                                                         Course Ratings are calculated from individual students’ ratings and a variety of other signals, like age of rating and reliability, to ensure that they reflect course quality fairly and accurately.                                                                                                            151 students enrolled                                                                    "
df <- data.frame(example)

如您所见，第一个观察结果由一个字符串组成，该字符串包含4个不同的部分：评分（4.6），评分数量（19个评分），一个句子（准确地……课程）和所招生的学生（151）

我使用separate()函数将该列分为4个：

df1 <- separate(df, example, c("Rating", "Number of rating", "Sentence", "Students"), sep = "     ")

因此，这与预期不符。

任何想法。

更新：

这就是您对@nicola的评论

> df1 <- separate(df, example, c("Rating", "Number of rating", "Sentence", "Students"), sep=" {4,}")
Warning message:
Expected 4 pieces. Additional pieces discarded in 1 rows [1].

Answer 1

如何？

x <- str_split(example, "  ") %>%
    unlist()
x <- x[x != ""]
df <- tibble("a", "b", "c", "d")
df[1, ] <- x
colnames(df) <- c("Rating", "Number of rating", "Sentence", "Students")

> str(df)
Classes ‘tbl_df’, ‘tbl’ and 'data.frame':   1 obs. of  4 variables:
 $ Rating          : chr "4.6"
 $ Number of rating: chr " (19 ratings)"
 $ Sentence        : chr " Course Ratings are calculated from individual students’ ratings and a variety of other signals, like age of ra"| __truncated__
 $ Students        : chr "151 students enrolled"

Answer 2

答案有两个键。首先是使用正确的正则表达式作为分隔符sep = "[[:space:]]{2,}"，这意味着两个或更多个空格（\\s{2,}是更常见的替代形式）。第二个是您的示例实际上有很多结尾的空格，separate()试图将其放在另一列中。只需使用trimws()即可将其删除。因此，解决方案如下所示：

library(tidyr)
library(dplyr)

example <- "4.6             (19 ratings)                                                         Course Ratings are calculated from individual students’ ratings and a variety of other signals, like age of rating and reliability, to ensure that they reflect course quality fairly and accurately.                                                                                                            151 students enrolled                                                                    "
df <- data.frame(example)

df_new <- df %>%
  mutate(example = trimws(example)) %>% 
  separate(col = "example", 
           into = c("rating", "number_of_ratings", "sentence", "students_enrolled"), 
           sep = "[[:space:]]{2,}")




as_tibble(df_new)
    # A tibble: 1 x 4
      rating number_of_ratings sentence                                                                    students_enrolled
      <chr>  <chr>             <chr>                                                                       <chr>            
    1 4.6    (19 ratings)      Course Ratings are calculated from individual students’ ratings and a vari~ 151 students enr~

tibble仅用于格式化输出。

Answer 3

使用stringr包和一些正则表达式当然可以实现：

  rating_mean n_ratings n_students                         descr
1        4.65        19        151    "Course (...) accurately."

代码

library(stringr)

# create result data frame
result <- data.frame(cbind(rating_mean = 0, n_ratings = 0, n_students = 0, descr = 0))

# loop through rows of example data frame
for (i in 1:nrow(df)){
    # replace spaces
    example[i, 1] <- gsub("\\s+", " ", example[i, 1])
    # match and extract mean rating
    result[i, 1] <- as.numeric(str_match(example[i], "^[0-9]+\\.[0-9]+"))
    # match and extract number of ratings
    result[i, 2] <- as.numeric(str_match(str_match(example[i, 1], "\\(.+\\)"), "[0-9]+"))
    # match and extract number of enrolled students
    result[i, 3] <- as.numeric(str_match(str_match(example[i, 1], "\\s[0-9].+$"), "[0-9]+"))
    # match and extract sentence
    result[i, 4] <- str_match(example[i, 1], "[A-Z].+\\.")
}

数据

example <- "4.65             (19 ratings)                                                         Course Ratings are calculated from individual students’ ratings and a variety of other signals, like age of rating and reliability, to ensure that they reflect course quality fairly and accurately.                                                                                                            151 students enrolled                                                                    "
example <- data.frame(example, stringsAsFactors = FALSE)

在R中的字符串中使用大空格分隔列

3 个答案:

代码

数据