Question

### The sample data

df <- data.frame(months = c('jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec'),
                 values = sample(100:200, 12, replace = TRUE))

### Load the library needed

library(dplyr)

我尝试了以下方法将三个字母的月份（例如jan）转换为日期：

df.1 <- mutate(df, year = 2015)
df.1 <- mutate(df.1, dates = sapply(months, function(x) grep(paste("(?i)", x, sep = ""), month.abb)))
df.1 <- mutate(df.1, dates1 = paste(dates, year, sep = "-"))
df.1 <- mutate(df.1, dates2 = as.Date(df.1$dates1, "%m-%Y"))

但是dates2列产生了NA，但是当我检查结构时，结果是：

> str(df.1)
'data.frame':   12 obs. of  6 variables:
 $ months: Factor w/ 12 levels "apr","aug","dec",..: 5 4 8 1 9 7 6 2 12 11 ...
 $ values: int  141 147 176 189 113 181 149 114 121 191 ...
 $ year  : num  2015 2015 2015 2015 2015 ...
 $ dates : int  1 2 3 4 5 6 7 8 9 10 ...
 $ dates1: chr  "1-2015" "2-2015" "3-2015" "4-2015" ...
 $ dates2: Date, format: NA NA NA NA ..

有没有办法将months列转换为日期类？怎么样？谢谢你的帮助。

Answer 1

据我所知，您不能使用as.Date或任何类似的功能将月份转换为该月份的日期实体。您必须提供更多信息，例如一天，即

as.Date("26jan","%d%b")
[1] "2017-01-26"

或使用如下功能：

library(zoo)
as.yearmon("jan","%b")
[1] "Jan 2017"

所以对于你的表达式来说，虽然不确定代码的用途，但是在这里你会去：

df <- data.frame(months = c('jan', 'feb', 'mar', 'apr', 'may', 'jun', 'jul', 'aug', 'sep', 'oct', 'nov', 'dec'),
                 values = sample(100:200, 12, replace = TRUE))


df.1 <- mutate(df, year = 2015)
df.1 <- mutate(df.1, dates = sapply(months, function(x) grep(paste("(?i)", x, sep = ""), month.abb)))
df.1 <- mutate(df.1, dates1 = paste(year,dates, sep = "-"))
df.1 <- mutate(df.1, dates2 = yearmon(df.1$dates1, "%Y-%m"))

as.yearmon(df.1$dates1)

[1] "Jan 2015" "Feb 2015" "Mar 2015" "Apr 2015" "May 2015" "Jun 2015" "Jul 2015" "Aug 2015" "Sep 2015" "Oct 2015"
[11] "Nov 2015" "Dec 2015"

Answer 2

感谢Nadizan's answer指出day方面，所以我重新构建了我的语法，如下所示：

df.1 <- mutate(df, year = "1-2015")
df.1 <- mutate(df.1, dates = sapply(months, function(x) grep(paste("(?i)", x, sep = ""), month.abb)))
df.1 <- mutate(df.1, dates1 = paste(dates, year, sep = "-"))
df.1 <- mutate(df.1, dates2 = as.Date(df.1$dates1, "%m-%d-%Y"))

然后我检查了结构，结果是：

> str(df.1)
'data.frame':   12 obs. of  6 variables:
 $ months: Factor w/ 12 levels "apr","aug","dec",..: 5 4 8 1 9 7 6 2 12 11 ...
 $ values: int  110 154 200 110 105 179 139 173 153 197 ...
 $ year  : chr  "1-2015" "1-2015" "1-2015" "1-2015" ...
 $ dates : int  1 2 3 4 5 6 7 8 9 10 ...
 $ dates1: chr  "1-1-2015" "2-1-2015" "3-1-2015" "4-1-2015" ...
 $ dates2: Date, format: "2015-01-01" "2015-02-01" "2015-03-01" "2015-04-01" ...

在r

2 个答案: