如何重塑数据框中的日期列？

Question

我想在同一个月内重塑我的日期列。例如，dataframe 的 Date 列的前 12 行包含 2001 年所有月份的字符以及相应年份本身。接下来的行是相同的，直到 2017 年。

因此。我想像下面这样重塑我的数据。例如，我希望所有年份的所有一月都在Date 列的第一行，然后是下一行的所有二月，所有年份的三月等等，直到所有年份的十二月（2001-2017）

我需要这样的格式：

1  2001     1
2  2002     1
3  2003     1
4  2004     1
5  2005     1
6  2006     1
7  2007     1
8  2008     1
9  2009     1
10 2010     1
11 2011     1
12 2012     1
13 2013     1
14 2014     1
15 2015     1
16 2016     1
17 2017     1
18 2001     2
19 2002     2
20 2003     2
21 2004     2
22 2005     2
23 2006     2
24 2007     2

这是我使用dput()生成的数据框

 #load packages that might be required
> library(tidyverse)
> library(xts)

> # Read NDVI 
> NDVI <- read.csv("processed//NDVI.csv")
> dput(NDVI)
structure(list(Date = c("Jan 1, 2001", "Feb 1, 2001", "Mar 1, 2001", 
"Apr 1, 2001", "May 1, 2001", "Jun 1, 2001", "Jul 1, 2001", "Aug 1, 2001", 
"Sep 1, 2001", "Oct 1, 2001", "Nov 1, 2001", "Dec 1, 2001", "Jan 1, 2002", 
"Feb 1, 2002", "Mar 1, 2002", "Apr 1, 2002", "May 1, 2002", "Jun 1, 2002", 
"Jul 1, 2002", "Aug 1, 2002", "Sep 1, 2002", "Oct 1, 2002", "Nov 1, 2002", 
"Dec 1, 2002", "Jan 1, 2003", "Feb 1, 2003", "Mar 1, 2003", "Apr 1, 2003", 
"May 1, 2003", "Jun 1, 2003", "Jul 1, 2003", "Aug 1, 2003", "Sep 1, 2003", 
"Oct 1, 2003", "Nov 1, 2003", "Dec 1, 2003", "Jan 1, 2004", "Feb 1, 2004", 
"Mar 1, 2004", "Apr 1, 2004", "May 1, 2004", "Jun 1, 2004", "Jul 1, 2004", 
"Aug 1, 2004", "Sep 1, 2004", "Oct 1, 2004", "Nov 1, 2004", "Dec 1, 2004", 
"Jan 1, 2005", "Feb 1, 2005", "Mar 1, 2005", "Apr 1, 2005", "May 1, 2005", 
"Jun 1, 2005", "Jul 1, 2005", "Aug 1, 2005", "Sep 1, 2005", "Oct 1, 2005", 
"Nov 1, 2005", "Dec 1, 2005", "Jan 1, 2006", "Feb 1, 2006", "Mar 1, 2006", 
"Apr 1, 2006", "May 1, 2006", "Jun 1, 2006", "Jul 1, 2006", "Aug 1, 2006", 
"Sep 1, 2006", "Oct 1, 2006", "Nov 1, 2006", "Dec 1, 2006", "Jan 1, 2007", 
"Feb 1, 2007", "Mar 1, 2007", "Apr 1, 2007", "May 1, 2007", "Jun 1, 2007", 
"Jul 1, 2007", "Aug 1, 2007", "Sep 1, 2007", "Oct 1, 2007", "Nov 1, 2007", 
"Dec 1, 2007", "Jan 1, 2008", "Feb 1, 2008", "Mar 1, 2008", "Apr 1, 2008", 
"May 1, 2008", "Jun 1, 2008", "Jul 1, 2008", "Aug 1, 2008", "Sep 1, 2008", 
"Oct 1, 2008", "Nov 1, 2008", "Dec 1, 2008", "Jan 1, 2009", "Feb 1, 2009", 
"Mar 1, 2009", "Apr 1, 2009", "May 1, 2009", "Jun 1, 2009", "Jul 1, 2009", 
"Aug 1, 2009", "Sep 1, 2009", "Oct 1, 2009", "Nov 1, 2009", "Dec 1, 2009", 
"Jan 1, 2010", "Feb 1, 2010", "Mar 1, 2010", "Apr 1, 2010", "May 1, 2010", 
"Jun 1, 2010", "Jul 1, 2010", "Aug 1, 2010", "Sep 1, 2010", "Oct 1, 2010", 
"Nov 1, 2010", "Dec 1, 2010", "Jan 1, 2011", "Feb 1, 2011", "Mar 1, 2011", 
"Apr 1, 2011", "May 1, 2011", "Jun 1, 2011", "Jul 1, 2011", "Aug 1, 2011", 
"Sep 1, 2011", "Oct 1, 2011", "Nov 1, 2011", "Dec 1, 2011", "Jan 1, 2012", 
"Feb 1, 2012", "Mar 1, 2012", "Apr 1, 2012", "May 1, 2012", "Jun 1, 2012", 
"Jul 1, 2012", "Aug 1, 2012", "Sep 1, 2012", "Oct 1, 2012", "Nov 1, 2012", 
"Dec 1, 2012", "Jan 1, 2013", "Feb 1, 2013", "Mar 1, 2013", "Apr 1, 2013", 
"May 1, 2013", "Jun 1, 2013", "Jul 1, 2013", "Aug 1, 2013", "Sep 1, 2013", 
"Oct 1, 2013", "Nov 1, 2013", "Dec 1, 2013", "Jan 1, 2014", "Feb 1, 2014", 
"Mar 1, 2014", "Apr 1, 2014", "May 1, 2014", "Jun 1, 2014", "Jul 1, 2014", 
"Aug 1, 2014", "Sep 1, 2014", "Oct 1, 2014", "Nov 1, 2014", "Dec 1, 2014", 
"Jan 1, 2015", "Feb 1, 2015", "Mar 1, 2015", "Apr 1, 2015", "May 1, 2015", 
"Jun 1, 2015", "Jul 1, 2015", "Aug 1, 2015", "Sep 1, 2015", "Oct 1, 2015", 
"Nov 1, 2015", "Dec 1, 2015", "Jan 1, 2016", "Feb 1, 2016", "Mar 1, 2016", 
"Apr 1, 2016", "May 1, 2016", "Jun 1, 2016", "Jul 1, 2016", "Aug 1, 2016", 
"Sep 1, 2016", "Oct 1, 2016", "Nov 1, 2016", "Dec 1, 2016", "Jan 1, 2017", 
"Feb 1, 2017", "Mar 1, 2017", "Apr 1, 2017", "May 1, 2017", "Jun 1, 2017", 
"Jul 1, 2017", "Aug 1, 2017", "Sep 1, 2017", "Oct 1, 2017", "Nov 1, 2017", 
"Dec 1, 2017"), NDVI = c(0.722, 0.418, 0.435, 0.568, 0.616, 0.75, 
0.62, 0.516, 0.389, 0.484, 0.65, 0.7, 0.533, 0.327, 0.279, 0.43, 
0.701, 0.797, 0.748, 0.569, 0.597, 0.662, 0.794, 0.706, 0.537, 
0.338, 0.404, 0.461, 0.759, 0.76, 0.578, 0.408, 0.56, 0.62, 0.684, 
0.785, 0.539, 0.442, 0.307, 0.461, 0.593, 0.739, 0.674, 0.495, 
0.603, 0.712, 0.776, 0.665, 0.522, 0.333, 0.398, 0.28, 0.713, 
0.746, 0.757, 0.549, 0.711, 0.685, 0.693, 0.716, 0.617, 0.476, 
0.407, 0.325, 0.555, 0.757, 0.622, 0.544, 0.452, 0.586, 0.761, 
0.649, 0.635, 0.472, 0.351, 0.402, 0.662, 0.757, 0.712, 0.69, 
0.618, 0.632, 0.797, 0.778, 0.543, 0.401, 0.393, 0.556, 0.68, 
0.784, 0.659, 0.654, 0.412, 0.653, 0.694, 0.727, 0.715, 0.55, 
0.641, 0.443, 0.709, 0.818, 0.646, 0.59, 0.39, 0.562, 0.67, 0.56, 
0.476, 0.312, 0.349, 0.405, 0.705, 0.766, 0.665, 0.577, 0.614, 
0.518, 0.718, 0.779, 0.792, 0.547, 0.585, 0.373, 0.605, 0.715, 
0.779, 0.758, 0.751, 0.77, 0.752, 0.805, 0.521, 0.471, 0.561, 
0.595, 0.688, 0.74, 0.77, 0.69, 0.704, 0.613, 0.653, 0.803, 0.63, 
0.472, 0.589, 0.512, 0.562, 0.699, 0.814, 0.637, 0.395, 0.462, 
0.419, 0.742, 0.498, 0.35, 0.308, 0.321, 0.597, 0.677, 0.729, 
0.526, 0.394, 0.567, 0.806, 0.752, 0.703, 0.495, 0.453, 0.48, 
0.593, 0.731, 0.799, 0.619, 0.403, 0.396, 0.556, 0.743, 0.717, 
0.504, 0.408, 0.356, 0.215, 0.68, 0.487, 0.594, 0.392, 0.566, 
0.547, 0.632, 0.604, 0.528, 0.424, 0.627, 0.448, 0.788, 0.764, 
0.592, 0.517, 0.274, 0.577, 0.754)), class = "data.frame", row.names = c(NA, 
-204L))

Answer 1

library(dplyr)
library(tidyr)
library(lubridate)
df %>%
  mutate(Date = mdy(Date)) %>%
  separate(Date, into = c("year", "month", "day"), remove = FALSE) %>%
  arrange(month, day, year)
#           Date year month day  NDVI
# 1   2001-01-01 2001    01  01 0.722
# 2   2002-01-01 2002    01  01 0.533
# 3   2003-01-01 2003    01  01 0.537
# 4   2004-01-01 2004    01  01 0.539
# 5   2005-01-01 2005    01  01 0.522
# 6   2006-01-01 2006    01  01 0.617
# ...

这通常不称为“重塑”操作 - 这是排序/排序/排列行。重塑/透视是当某物是一列变成一行时，反之亦然。