英文:
Convert the quarter date column with the last day of each quarter to the first day of each quarter, or vice versa
问题
df1：
df1 <- structure(list(date = c("2010-3-31", "2010-6-30", "2010-9-30", "2010-12-31", "2011-3-31", "2011-6-30", "2011-9-30", "2011-12-31"), value = c(24.1, 16.4, 18.5, 8.61, 12.6, 20.1, 17.9, 14.5)), class = "data.frame", row.names = c(NA, -8L))
df2：
df2 <- structure(list(date = c("2010-1-1", "2010-4-1", "2010-7-1", "2010-10-1", "2011-1-1", "2011-4-1", "2011-7-1", "2011-10-1"), value = c(24.1, 16.4, 18.5, 8.61, 12.6, 20.1, 17.9, 14.5)), class = "data.frame", row.names = c(NA, -8L))
英文:
Suppose I have the following df1 or df2, how can I use R to convert the last day of each quarter to the first day of each quarter in date column, or vice versa? Thanks.
df1:
df1 <- structure(list(date = c("2010-3-31", "2010-6-30", "2010-9-30",
"2010-12-31", "2011-3-31", "2011-6-30", "2011-9-30", "2011-12-31"
), value = c(24.1, 16.4, 18.5, 8.61, 12.6, 20.1, 17.9, 14.5)), class = "data.frame", row.names = c(NA,
-8L))
Out:
date value
1 2010-3-31 24.10
2 2010-6-30 16.40
3 2010-9-30 18.50
4 2010-12-31 8.61
5 2011-3-31 12.60
6 2011-6-30 20.10
7 2011-9-30 17.90
8 2011-12-31 14.50
df2:
df2 <- structure(list(date = c("2010-1-1", "2010-4-1", "2010-7-1", "2010-10-1",
"2011-1-1", "2011-4-1", "2011-7-1", "2011-10-1"), value = c(24.1,
16.4, 18.5, 8.61, 12.6, 20.1, 17.9, 14.5)), class = "data.frame", row.names = c(NA,
-8L))
Out:
date value
1 2010-1-1 24.10
2 2010-4-1 16.40
3 2010-7-1 18.50
4 2010-10-1 8.61
5 2011-1-1 12.60
6 2011-4-1 20.10
7 2011-7-1 17.90
8 2011-10-1 14.50
答案1
得分: 1
1) 将一个yearqtr对象转换为Date类将给出该季度的第一天：
library(dplyr)
library(zoo)
df1 %>%
mutate(date = as.Date(as.yearqtr(as.Date(date))))
结果如下：
date value
1 2010-01-01 24.10
2 2010-04-01 16.40
3 2010-07-01 18.50
4 2010-10-01 8.61
5 2011-01-01 12.60
6 2011-04-01 20.10
7 2011-07-01 17.90
8 2011-10-01 14.50
2) 要获取季度的末尾，请注意as.Date.yearqtr有一个frac=参数，它的默认值为0（表示季度的开始），1表示季度的末尾，或任何分数值。
df2 %>%
mutate(date = as.Date(as.yearqtr(as.Date(date)), frac = 1))
结果如下：
date value
1 2010-03-31 24.10
2 2010-06-30 16.40
3 2010-09-30 18.50
4 2010-12-31 8.61
5 2011-03-31 12.60
6 2011-06-30 20.10
7 2011-09-30 17.90
8 2011-12-31 14.50
3) 另一种可能性是，不是将季度表示为日期，而是直接表示为yearqtr对象。 yearqtr对象内部表示为年份 + 0, 1/4, 1/2, 3/4分别代表四个季度，因此可以轻松进行操作和排序，例如，如果yq是一个yearqtr对象，yq+1/4代表下一个季度。
df1 %>%
mutate(date = as.yearqtr(as.Date(date)))
结果如下：
date value
1 2010 Q1 24.10
2 2010 Q2 16.40
3 2010 Q3 18.50
4 2010 Q4 8.61
5 2011 Q1 12.60
6 2011 Q2 20.10
7 2011 Q3 17.90
8 2011 Q4 14.50
英文:
1) Converting a yearqtr object to Date class will give the first of the quarter so
library(dplyr)
library(zoo)
df1 %>%
mutate(date = as.Date(as.yearqtr(as.Date(date))))
giving:
date value
1 2010-01-01 24.10
2 2010-04-01 16.40
3 2010-07-01 18.50
4 2010-10-01 8.61
5 2011-01-01 12.60
6 2011-04-01 20.10
7 2011-07-01 17.90
8 2011-10-01 14.50
2) To get the end of quarter note that as.Date.yearqtr has a frac= argument which is 0 (default) for beginning of quarter, 1 for end of quarter or any fraction between.
df2 %>%
mutate(date = as.Date(as.yearqtr(as.Date(date)), frac = 1))
giving:
date value
1 2010-03-31 24.10
2 2010-06-30 16.40
3 2010-09-30 18.50
4 2010-12-31 8.61
5 2011-03-31 12.60
6 2011-06-30 20.10
7 2011-09-30 17.90
8 2011-12-31 14.50
3) Another possibility is, rather than representing the quarter by a date to represent it directly as a yearqtr object. yearqtr objects are internally year + 0, 1/4, 1/2, 3/4 for the 4 quarters so they can be easily manipulated and sorted, e.g. if yq is a yearqtr object yq+1/4 is the quarter following.
df1 %>%
mutate(date = as.yearqtr(as.Date(date)))
giving:
date value
1 2010 Q1 24.10
2 2010 Q2 16.40
3 2010 Q3 18.50
4 2010 Q4 8.61
5 2011 Q1 12.60
6 2011 Q2 20.10
7 2011 Q3 17.90
8 2011 Q4 14.50
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