1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
|
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/date.R
\name{date-count-between}
\alias{date-count-between}
\alias{date_count_between.Date}
\title{Counting: date}
\usage{
\method{date_count_between}{Date}(start, end, precision, ..., n = 1L)
}
\arguments{
\item{start, end}{\verb{[Date]}
A pair of date vectors. These will be recycled to their common
size.}
\item{precision}{\verb{[character(1)]}
One of:
\itemize{
\item \code{"year"}
\item \code{"quarter"}
\item \code{"month"}
\item \code{"week"}
\item \code{"day"}
}}
\item{...}{These dots are for future extensions and must be empty.}
\item{n}{\verb{[positive integer(1)]}
A single positive integer specifying a multiple of \code{precision} to use.}
}
\value{
An integer representing the number of \code{precision} units between
\code{start} and \code{end}.
}
\description{
This is a Date method for the \code{\link[=date_count_between]{date_count_between()}} generic.
\code{date_count_between()} counts the number of \code{precision} units between
\code{start} and \code{end} (i.e., the number of years or months). This count
corresponds to the \emph{whole number} of units, and will never return a
fractional value.
This is suitable for, say, computing the whole number of years or months
between two dates, accounting for the day of the month.
\emph{Calendrical based counting:}
These precisions convert to a year-month-day calendar and count while in that
type.
\itemize{
\item \code{"year"}
\item \code{"quarter"}
\item \code{"month"}
}
\emph{Time point based counting:}
These precisions convert to a time point and count while in that type.
\itemize{
\item \code{"week"}
\item \code{"day"}
}
For dates, whether a calendar or time point is used is not all that
important, but is is fairly important for date-times.
}
\details{
\code{"quarter"} is equivalent to \code{"month"} precision with \code{n} set to \code{n * 3L}.
}
\section{Comparison Direction}{
The computed count has the property that if \code{start <= end}, then
\verb{start + <count> <= end}. Similarly, if \code{start >= end}, then
\verb{start + <count> >= end}. In other words, the comparison direction between
\code{start} and \code{end} will never change after adding the count to \code{start}. This
makes this function useful for repeated count computations at
increasingly fine precisions.
}
\examples{
start <- date_parse("2000-05-05")
end <- date_parse(c("2020-05-04", "2020-05-06"))
# Age in years
date_count_between(start, end, "year")
# Number of "whole" months between these dates. i.e.
# `2000-05-05 -> 2020-04-05` is 239 months
# `2000-05-05 -> 2020-05-05` is 240 months
# Since 2020-05-04 occurs before the 5th of that month,
# it gets a count of 239
date_count_between(start, end, "month")
# Number of "whole" quarters between (same as `"month"` with `n * 3`)
date_count_between(start, end, "quarter")
date_count_between(start, end, "month", n = 3)
# Number of days between
date_count_between(start, end, "day")
# Number of full 3 day periods between these two dates
date_count_between(start, end, "day", n = 3)
# Essentially the truncated value of this
date_count_between(start, end, "day") / 3
# ---------------------------------------------------------------------------
# Breakdown into full years, months, and days between
x <- start
years <- date_count_between(x, end, "year")
x <- add_years(x, years)
months <- date_count_between(x, end, "month")
x <- add_months(x, months)
days <- date_count_between(x, end, "day")
x <- add_days(x, days)
data.frame(
start = start,
end = end,
years = years,
months = months,
days = days
)
# Note that when breaking down a date like that, you may need to
# set `invalid` during intermediate calculations
start <- date_build(2019, c(3, 3, 4), c(30, 31, 1))
end <- date_build(2019, 5, 05)
# These are 1 month apart (plus a few days)
months <- date_count_between(start, end, "month")
# But adding that 1 month to `start` results in an invalid date
try(add_months(start, months))
# You can choose various ways to resolve this
start_previous <- add_months(start, months, invalid = "previous")
start_next <- add_months(start, months, invalid = "next")
days_previous <- date_count_between(start_previous, end, "day")
days_next <- date_count_between(start_next, end, "day")
# Resulting in slightly different day values.
# No result is "perfect". Choosing "previous" or "next" both result
# in multiple `start` dates having the same month/day breakdown values.
data.frame(
start = start,
end = end,
months = months,
days_previous = days_previous,
days_next = days_next
)
}
|
