拆分字符串并在每个数字之前添加断线

Question

所以我有向量，里面有参考书目

bibliography <- c("1. Cohen, A. C. (1955). Restriction and selection insamples from bivariate normal distributions. Journal
of the American Statistical Association, 50, 884–893.  2.Breslow, N. E. and Cain, K. C. (1988). Logistic regression for the two-stage case-control data.
Biometrika, 75, 11–20.  3.Arismendi, J. C. (2013). Multivariate truncated moments. Journal of Multivariate Analysis, 117, 41–75")

我想在表示编号的每一个数字(即1、2和3 )之前添加新的行/换行()。因此，如果我有50条书目，我想用向量自动拆分所有字符串，并在表示编号的每个数字之前添加断线。

到目前为止，我已经尝试过这样的方法(这不是最好的选择，因为第三个参考书目被忽略了)：

   bibliography <- unlist(strsplit(bibliography, "  "))
    bibliography <- bibliography[-length(bibliography)] <- paste0(bibliography[-length(bibliography)], ' \\\\ ')

输出是这样的(，这是我想要的输出)：

   [1] "1. Cohen, A. C. (1955). Restriction and selection in samples from bivariate normal distributions. Journal\nof the American Statistical Association, 50, 884–893. \\\\ "
    [2] "2.Breslow, N. E. and Cain, K. C. (1988). Logistic regression for the two-stage case-control data.\nBiometrika, 75, 11–20. \\\\ "

但这很费时，因为我不得不在每个数字(即1和2)之前手动添加双空间。这段代码才能正常工作。

我也看过这里

Add new line before every number in a string

Inserting Newline character before every number occurring in a string?

Answer 1

这样你就可以得到你想要的地方了：

library(stringr)
library(dplyr)

# The first line adds the "~" character at the right break point
str_split(gsub("([1-9]\\.[]*[A-Z])","~\\1",bibliography), "~") %>%
unlist()  %>%
str_trim(side = c("both")) # Trimming potential spaces at the strings sides

Answer 2

我尝试了一种基于正则表达式的方法

bibliography <- c("1. Cohen, A. C. (1955). Restriction and selection insamples from bivariate normal distributions. Journal of the American Statistical Association, 50, 884–893.  2.Breslow, N. E. and Cain, K. C. (1988). Logistic regression for the two-stage case-control data.
                  Biometrika, 75, 11–20.  3.Arismendi, J. C. (2013). Multivariate truncated moments. Journal of Multivariate Analysis, 117, 41–75")

out <- gsub("([^0-9][0-9]{1}\\.|^[0-9]{1}\\.)", "\t\\1",bibliography)
out <- unlist(strsplit(out, "\t"))
out <- gsub("^\\s+|\\s+$", "", out)
out <- out[-1]

你也许可以试一试。