从数据框的某一列获取最频繁的字符串

Question

从数据框的某一列获取最频繁的字符串

3

我需要返回一个字符串出现次数最多的前n个结果，输入为多行数据框架。所有的值都在同一列中，名为“MissingDates”。

以下是示例数据，总共大约有5000行：

Symbol Count  MissingDates     
AD  27  1995-12-26, 1996-01-02, 1996-04-26, 1996-04-30, 1996-05-06, 1996-08-26, 1996-09-03, 1996-09-04, 1996-10-11, 1996-11-13, 1996-11-29, 1996-12-09, 1996-12-20, 1996-12-23, 1996-12-26, 1996-12-27, 1997-01-02, 1997-05-02, 1997-09-10, 1998-01-02, 1998-04-16, 1998-12-08, 1999-12-27, 1999-12-31, 2001-09-12, 2003-08-06, 2003-10-13
BP  14  1995-08-09, 1995-08-15, 1995-12-26, 1996-01-02, 1996-09-06, 1996-12-26, 1997-01-02, 1997-12-26, 1998-01-02, 1998-04-16, 2001-09-12, 2002-12-24, 2003-08-06, 2003-10-13
C   3   1999-12-31, 2001-12-24, 2002-12-24
CC  285 1994-05-18, 1994-05-19, 1994-05-20, 1994-05-23, 1994-05-24, 1994-05-25, 1994-05-26, 1994-05-27, 1994-05-31, 1994-06-01, 1994-06-02, 1994-06-03, 1994-06-06, 1994-06-07, 1994-06-08, 1994-06-09, 1994-06-10, 1994-06-13, 1994-06-14, 1994-06-15, 1994-06-16, 1994-06-17, 1994-06-20, 1994-06-21, 1994-06-23, 1994-06-24, 1994-06-27, 1994-06-28, 1994-06-29, 1994-06-30, 1994-07-01, 1994-07-06, 1994-07-14, 1994-07-15, 1994-07-18, 1994-07-19, 1994-07-21, 1994-07-25, 1994-07-27, 1994-07-28, 1994-08-03, 1994-08-04, 1994-08-08, 1994-08-09, 1994-08-10, 1994-08-11, 1994-08-12, 1994-08-15, 1994-08-17, 1994-08-18, 1994-08-19, 1994-08-22, 1994-08-23, 1994-08-24, 1994-08-25, 1994-08-29, 1994-08-31, 1994-09-01, 1994-09-02, 1994-09-06, 1994-09-07, 1994-09-08, 1994-09-09, 1994-09-12, 1994-09-13, 1994-09-15, 1994-09-16, 1994-09-19, 1994-09-20, 1994-09-21, 1994-09-22, 1994-09-23, 1994-09-27, 1994-09-28, 1994-09-29, 1994-09-30, 1994-10-03, 1994-10-04, 1994-10-06, 1994-10-14, 1994-10-18, 1994-10-19, 1994-10-25, 1994-10-26, 1994-10-27, 1994-10-28, 1994-10-31, 1994-11-01, 1994-11-09, 1994-11-10, 1994-11-11, 1994-11-16, 1994-11-17, 1994-11-25, 1994-11-28, 1994-12-01, 1994-12-02, 1994-12-06, 1994-12-07, 1994-12-08, 1994-12-09, 1994-12-12, 1994-12-13, 1994-12-14, 1994-12-15, 1994-12-16, 1994-12-23, 1994-12-27, 1994-12-29, 1994-12-30, 1995-01-03, 1995-01-05, 1995-01-09, 1995-01-11, 1995-01-13, 1995-01-16, 1995-01-17, 1995-01-18, 1995-01-19, 1995-01-20, 1995-01-24, 1995-01-25, 1995-02-13, 1995-02-17, 1995-05-01, 1995-07-03, 1995-11-24, 1995-12-26, 1996-01-08, 1996-01-09, 1996-07-05, 1996-11-29, 1996-12-26, 1997-11-28, 1997-12-26, 1998-01-02, 1998-11-27, 1999-06-17, 1999-06-18, 1999-06-21, 1999-06-22, 1999-06-23, 1999-06-24, 1999-06-25, 1999-06-28, 1999-06-29, 1999-06-30, 1999-07-01, 1999-07-02, 1999-07-06, 1999-07-07, 1999-07-08, 1999-07-09, 1999-07-12, 1999-07-13, 1999-07-14, 1999-07-15, 1999-07-16, 1999-07-19, 1999-07-20, 1999-07-21, 1999-07-22, 1999-07-23, 1999-07-26, 1999-07-27, 1999-07-28, 1999-07-29, 1999-07-30, 1999-08-02, 1999-08-03, 1999-08-04, 1999-08-05, 1999-08-06, 1999-08-09, 1999-08-10, 1999-08-11, 1999-08-12, 1999-08-13, 1999-08-16, 1999-08-17, 1999-08-18, 1999-08-19, 1999-08-20, 1999-08-23, 1999-08-24, 1999-08-25, 1999-08-26, 1999-08-27, 1999-08-30, 1999-08-31, 1999-09-01, 1999-09-02, 1999-09-03, 1999-09-07, 1999-09-08, 1999-09-09, 1999-09-10, 1999-09-13, 1999-09-14, 1999-09-15, 1999-09-16, 1999-09-17, 1999-09-20, 1999-09-21, 1999-09-22, 1999-09-23, 1999-09-24, 1999-09-27, 1999-09-28, 1999-09-29, 1999-09-30, 1999-10-01, 1999-10-04, 1999-10-05, 1999-10-06, 1999-10-07, 1999-10-08, 1999-10-11, 1999-10-12, 1999-10-13, 1999-10-14, 1999-10-15, 1999-10-18, 1999-10-19, 1999-10-20, 1999-10-21, 1999-10-22, 1999-10-25, 1999-10-26, 1999-10-27, 1999-10-28, 1999-10-29, 1999-11-01, 1999-11-02, 1999-11-03, 1999-11-04, 1999-11-05, 1999-11-08, 1999-11-09, 1999-11-10, 1999-11-11, 1999-11-12, 1999-11-15, 1999-11-16, 1999-11-17, 1999-11-18, 1999-11-19, 1999-11-22, 1999-11-23, 1999-11-24, 1999-11-26, 1999-11-29, 1999-11-30, 1999-12-01, 1999-12-02, 1999-12-03, 1999-12-06, 1999-12-07, 1999-12-08, 1999-12-09, 1999-12-10, 1999-12-13, 1999-12-31, 2000-07-03, 2000-11-24, 2001-09-13, 2001-09-14, 2001-11-23, 2001-12-24, 2001-12-26, 2001-12-31, 2002-07-05, 2002-11-29, 2002-12-26, 2003-02-18, 2003-11-28, 2004-06-11, 2004-11-26, 2004-12-31, 2005-11-25, 2006-11-24, 2007-01-02, 2007-11-23, 2007-12-24, 2011-01-03
CD  14  1995-08-09, 1995-12-26, 1996-01-02, 1996-06-11, 1996-06-20, 1996-09-09, 1996-09-11, 1996-12-26, 1997-01-02, 1997-12-26, 1998-01-02, 1998-04-16, 2001-01-02, 2001-09-12
CT  154 1995-11-24, 1996-01-08, 1996-07-05, 1996-11-29, 1996-12-24, 1997-11-28, 1997-12-26, 1998-11-27, 1999-11-26, 1999-12-31, 2000-07-03, 2000-11-24, 2001-09-11, 2001-09-12, 2001-09-13, 2001-09-14, 2001-11-12, 2001-11-23, 2001-12-24, 2001-12-31, 2002-05-21, 2002-05-22, 2002-05-23, 2002-05-24, 2002-05-28, 2002-05-29, 2002-05-30, 2002-05-31, 2002-06-03, 2002-06-04, 2002-06-05, 2002-06-06, 2002-06-07, 2002-06-10, 2002-06-11, 2002-06-12, 2002-06-13, 2002-06-14, 2002-06-17, 2002-06-18, 2002-06-19, 2002-06-20, 2002-06-21, 2002-06-24, 2002-06-25, 2002-06-26, 2002-06-27, 2002-06-28, 2002-07-01, 2002-07-02, 2002-07-03, 2002-07-05, 2002-07-08, 2002-07-09, 2002-07-10, 2002-07-11, 2002-07-12, 2002-07-15, 2002-07-16, 2002-07-17, 2002-07-18, 2002-07-19, 2002-07-22, 2002-07-23, 2002-07-24, 2002-07-25, 2002-07-26, 2002-07-29, 2002-07-30, 2002-07-31, 2002-08-01, 2002-08-02, 2002-08-05, 2002-08-06, 2002-08-07, 2002-08-08, 2002-08-09, 2002-08-12, 2002-08-13, 2002-08-14, 2002-08-15, 2002-08-16, 2002-08-19, 2002-08-20, 2002-08-21, 2002-08-22, 2002-08-23, 2002-08-26, 2002-08-27, 2002-08-28, 2002-08-29, 2002-08-30, 2002-09-03, 2002-09-04, 2002-09-05, 2002-09-06, 2002-09-09, 2002-09-10, 2002-09-11, 2002-09-12, 2002-09-13, 2002-09-16, 2002-09-17, 2002-09-18, 2002-09-19, 2002-09-20, 2002-09-23, 2002-09-24, 2002-09-25, 2002-09-26, 2002-09-27, 2002-09-30, 2002-10-01, 2002-10-02, 2002-10-03, 2002-10-04, 2002-10-07, 2002-10-08, 2002-10-09, 2002-10-10, 2002-10-11, 2002-10-14, 2002-10-15, 2002-10-16, 2002-10-17, 2002-10-18, 2002-10-21, 2002-10-22, 2002-10-23, 2002-10-24, 2002-10-25, 2002-10-28, 2002-10-29, 2002-10-30, 2002-10-31, 2002-11-01, 2002-11-04, 2002-11-05, 2002-11-06, 2002-11-07, 2002-11-29, 2002-12-24, 2003-02-18, 2003-11-28, 2003-12-26, 2004-01-02, 2004-06-11, 2004-11-26, 2004-12-31, 2005-11-25, 2006-11-24, 2007-01-02, 2007-11-23, 2007-12-24

所以该函数将有一个传递的参数，它将从数据框中返回日期中最频繁出现的n个元素。

我看了一下which.max但是没能想出如何将其应用于多行（整个数据框列），或者给我多个日期（n）作为输出。

如果代码只需要单个输出值，那么这是可以接受的，作为我工作的起点。任何指针都将不胜感激。

这是一个pastebin，因为字符串太长而导致我遇到麻烦： http://pastebin.com/B1YPicC8

> str(gaps)
    'data.frame':   5560 obs. of  3 variables:
     $ Symbol      : 因子，共有5560个级别：“@AD#”，“@BP#”等
     $ Count       : 整数，表示每个符号的缺失数量
     $ MissingDates: 因子，共有3568个级别，表示缺失日期的列表，如“1995-12-26, 1996-01-02, 1996-04-26, 1996-04-30, 1996-05-06, 1996-08-26, 1996-09-03, 1996-09-04, 1996-10-11, 1996-11-13, 1996-11”| __truncated__,..

- ctrlbrk

如果它们都是日期，那么你可以只使用 table(data) 并从中按行获取最大值。 - Rich Scriven

它们是日期字符串，但不被归类为日期。我不需要最大值（最高/最近），我需要最频繁出现的值。 - ctrlbrk

@DavidArenburg 我尝试了那个命令，但输出结果有大约20,000行（head命令无效）。我认为这是因为在某些情况下，一行中可能有一千个或更多的日期，并且会自动换行。该列的格式是字符串“日期”，逗号空格<重复>。 - ctrlbrk

谢谢，我将其作为问题的编辑发布，并刚刚完成。 - ctrlbrk

好的，现在我明白你那里有什么了。你想要什么样的输出？你想要每行中最频繁出现的日期吗？还是整个列的最频繁日期？ - David Arenburg

显示剩余3条评论

2个回答

1

这里有另一个可能的解决方案。

设置一些数据，

set.seed(5)
ss1 <- sample(seq(s <- Sys.Date(), s+10, "day"), 20, TRUE)
ss2 <- sample(seq(s <- Sys.Date(), s+10, "day"), 20, TRUE)
ls1 <- list(ss1 = ss1, ss2 = ss2)

定义函数：

f <- function(x, n) sort(table(x), decreasing = TRUE)[1:n]

将函数应用于数据：

lapply(ls1, f, n = 3)
# $ss1
# x
# 2014-09-08 2014-09-09 2014-09-07 
#          3          3          2 
# 
# $ss2
# x
# 2014-09-10 2014-09-06 2014-09-07 
#          4          3          2

- Rich Scriven

我怀疑它在他的特定情况下是否有效。每一行不是单独条目的向量。请在他的数据上尝试您的函数。 - David Arenburg

我无法读取他的数据。缺失的日期是在一个字符串中吗？ - Rich Scriven

是的，缺失的日期是一个由单逗号分隔的字符串。 - ctrlbrk

网页内容由stack overflow 提供, 点击上面的

可以查看英文原文，
原文链接

- David Arenburg · Accepted Answer

似乎您需要类似以下内容的东西：

功能

freqfunc <- function(x, n){
  tail(sort(table(unlist(strsplit(as.character(x), ", ")))), n)
}

在您的数据集上进行测试

freqfunc(gaps$MissingDates, 5) # Five most frequent dates

## 1996-12-26 1997-12-26 1998-01-02 1999-12-31 2001-09-12 
##          4          4          4          4          4