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# mixtime <a href="https://pkg.mitchelloharawild.com/mixtime/"><img src="man/figures/logo.svg" align="right" height="139" alt="mixtime website" /></a>

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mixtime provides flexible time classes for time series analysis and
forecasting with mixed temporal granularities. It is designed for
handling temporal data at different frequencies, making it ideal for:

- Changing observation frequencies (e.g., historical quarterly records
  now reported monthly)
- Analysis involving data at different temporal resolutions (e.g.,
  quarterly tourism and monthly turnover)
- Forecasting with temporal reconciliation across multiple time scales

## Key Features

**📈 Linear Time** - Create linear time vectors with `linear_time()` or
with helpers:

- `year()`, `yearquarter()`, `yearmonth()`, `yearweek()`, `date()`,
  `datetime()`

**🔄 Cyclical Time** - Create cyclical time vectors with
`cyclical_time()` or with helpers:

- `month_of_year()`, `day_of_year()`, `day_of_month()`, `time_of_day()`,
  `day_of_week()`, `week_of_year()`

**⏳ Time durations** - Create time duration vectors with `duration()`
or with helpers:

- `years()`, `quarters()`, `months()`, `weeks()`, `days()`, `hours()`,
  `minutes()`, `seconds()`, `milliseconds()`

**🕰️ Temporal semantics**

- Discrete and continuous time models
- Timezone support for all chronons
- Custom granule sizes (e.g. `week(2L)` for fortnights)
- Mixed granularity vectors for different temporal resolution over time
  (or series)

**📅 Calendar Systems** - Support for several calendars:

- `cal_gregorian` - Gregorian dates (e.g. 2026-02-17)
- `cal_isoweek` - ISO week dates (e.g. 2026-W8-Tue)
- `cal_sym454` - Symmetry454 dates (e.g. 2026-Feb-W4-Tue)
- More calendars coming, including custom censored calendars

**🧮 Temporal Operations**

- Rounding: `time_floor()`, `time_round()`, `time_ceiling()`
- Sequencing: `seq()` for linear and cyclical time points

## Installation

The mixtime package can be installed from CRAN with:

``` r
install.packages("mixtime")
```

The development version can be installed from
[GitHub](https://github.com/mitchelloharawild/mixtime) with:

``` r
# install.packages("remotes")
remotes::install_github("mitchelloharawild/mixtime")
```

## Usage

``` r
library(mixtime)
#> 
#> Attaching package: 'mixtime'
#> The following objects are masked from 'package:base':
#> 
#>     date, months, quarters
demo_time <- as.POSIXct("2026-02-22 18:30:42", tz = "UTC")
demo_date <- as.Date("2026-02-22")
```

The mixtime package is designed around the time units of calendars.
These time units are used to create and manipulate time vectors.

### Calendars and time units

Calendars have a `cal_*` prefix, which contain a set of time units that
can be accessed with `<cal>$<unit>`. Using time units as functions
produces time granules.

``` r
# The Gregorian calendar
cal_gregorian
#> <cal_gregorian>
#> Time units:
#>   - year
#>   - quarter
#>   - month
#>   - day
#>   - ampm
#>   - hour
#>   - minute
#>   - second
#>   - millisecond

# A 1-month time granule
cal_gregorian$month(1L) # (1L is integer 1)
#> <mixtime::tu_month>
#>  @ n : int 1
#>  @ tz: 'mt_naive' chr NA

# A 2-week time granule (fortnights)
cal_isoweek$week(2L)
#> <mixtime::tu_week>
#>  @ n : int 2
#>  @ tz: 'mt_naive' chr NA
```

### Linear Time

A linear time vector uses time granules to define the resolution of time
points, known as a `chronon` (the smallest granules of time). When the
input time has a different resolution than the `chronon`, it will be
automatically converted.

``` r
linear_time(demo_date, chronon = cal_gregorian$month(1L))
#> <mixtime[1]>
#> [1] 2026 Feb
```

Discrete time models (integer-based values) are used by default, however
continuous time models (double-based values) can be used with
`discrete = FALSE` to allow fractional chronons.

``` r
# February 22nd is 75% through the month (in non-leap years)
linear_time(demo_date, chronon = cal_gregorian$month(1L), discrete = FALSE)
#> <mixtime[1]>
#> [1] 2026 Feb 75.0%
```

Linear time helper functions are available to quickly create common time
points.

``` r
# Create time vectors at different granularities
yearquarter(demo_date) + 0:7
#> <mixtime[8]>
#> [1] 2026 Q1 2026 Q2 2026 Q3 2026 Q4 2027 Q1 2027 Q2 2027 Q3 2027 Q4
yearmonth(demo_date) + 0:11
#> <mixtime[12]>
#>  [1] 2026 Feb 2026 Mar 2026 Apr 2026 May 2026 Jun 2026 Jul 2026 Aug 2026 Sep 2026 Oct 2026 Nov
#> [11] 2026 Dec 2027 Jan
yearweek(demo_date) + 0:10
#> <mixtime[11]>
#>  [1] 2026 W08 2026 W09 2026 W10 2026 W11 2026 W12 2026 W13 2026 W14 2026 W15 2026 W16 2026 W17
#> [11] 2026 W18
date(demo_date) + 0:6
#> <mixtime[7]>
#> [1] 2026-02-22 2026-02-23 2026-02-24 2026-02-25 2026-02-26 2026-02-27 2026-02-28
```

The mixtime package allows time of different granulities to be combined
in a single vector.

``` r
c(
  year(demo_date), yearquarter(demo_date), 
  yearmonth(demo_date), yearweek(demo_date)
)
#> <mixtime[4]>
#> [1] 2026     2026 Q1  2026 Feb 2026 W08
```

### Cyclical Time

A cyclical time vector is defined by two time granules: a `chronon` (the
smaller granule of time) and a `cycle` (the larger granule that the
`chronon` loops over).

``` r
# The `calendar` argument provides a masking scope to `chronon` and `cycle`
cyclical_time(demo_date, chronon = day(1L), cycle = week(1L), calendar = cal_isoweek)
#> <mixtime[1]>
#> [1] Sun
```

There are several cyclical time helper functions for convenience.

``` r
# Extract cyclical components
month_of_year(demo_date)
#> <mixtime[1]>
#> [1] Feb
week_of_year(demo_date)
#> <mixtime[1]>
#> [1] W08
day_of_week(demo_date)
#> <mixtime[1]>
#> [1] Sun

# Continuous cyclical time shows progress through chronons
day_of_week(demo_time, discrete = FALSE)
#> <mixtime[1]>
#> [1] Sun 77.1%
```

### Timezones

All linear and cyclical time vectors support timezones via the `tz`
argument.

``` r
demo_time
#> [1] "2026-02-22 18:30:42 UTC"
# Same day (Sunday) in LA
date(demo_time, tz = "America/Los_Angeles")
#> <mixtime[1]>
#> [1] 2026-02-22 PST
date(demo_time, tz = "America/Los_Angeles", discrete = FALSE)
#> <mixtime[1]>
#> [1] 2026-02-22 43.8% PST
day_of_week(demo_time, tz = "America/Los_Angeles")
#> <mixtime[1]>
#> [1] Sun PST

# Next day (Monday) in Melbourne (23% through the 23rd)
date(demo_time, tz = "Australia/Melbourne")
#> <mixtime[1]>
#> [1] 2026-02-23 AEDT
date(demo_time, tz = "Australia/Melbourne", discrete = FALSE)
#> <mixtime[1]>
#> [1] 2026-02-23 23.0% AEDT
day_of_week(demo_time, tz = "Australia/Melbourne")
#> <mixtime[1]>
#> [1] Mon AEDT
```

### Temporal Manipulation

Linear time points can be adjusted to the floor, ceiling, or rounded to
a specified time granule.

``` r
# Round dates to different granularities
time_floor(demo_date, cal_gregorian$month(1L))
#> [1] "2026-02-01"
time_round(demo_date, cal_isoweek$week(1L))
#> [1] "2026-02-23"
time_ceiling(demo_date, cal_gregorian$month(1L))
#> [1] "2026-03-01"
```

### Time Sequences

The `seq()` function creates sequences of time points iterating by a
given time granule.

``` r
# Integer increments (advances by chronon's natural granule)
seq(yearmonth(demo_date), by = 1L, length.out = 10)
#> <mixtime[10]>
#>  [1] 2026 Feb 2026 Mar 2026 Apr 2026 May 2026 Jun 2026 Jul 2026 Aug 2026 Sep 2026 Oct 2026 Nov

# Time can be sequenced by different granules than the chronon
seq(date(demo_date), by = cal_gregorian$month(1L), length.out = 8)
#> <mixtime[8]>
#> [1] 2026-02-22 2026-03-22 2026-04-22 2026-05-22 2026-06-22 2026-07-22 2026-08-22 2026-09-22
```
