`sjl_weighted()`

computes the **absolute social jetlag across all shifts**
for the shift version of the Munich ChronoType Questionnaire (MCTQ).

## Arguments

- sjl
A

`list`

object with`Duration`

elements corresponding to the**social jetlag in each shift**from a shift version of the MCTQ questionnaire (you can use`sjl()`

to compute it).`sjl`

elements and values must be paired with`n`

elements and values.- n_w
A

`list`

object with integerish`integer`

or`double`

elements corresponding to the**number of days worked in each shift within a shift cycle**from a shift version of the MCTQ questionnaire.`n`

elements and values must be paired with`sjl`

elements and values.

## Value

A `Duration`

object corresponding to the
vectorized weighted mean of `sjl`

with `n_w`

as weights.

## Details

**Standard MCTQ** functions were created following the guidelines in
Roenneberg, Wirz-Justice, & Merrow (2003), Roenneberg, Allebrandt, Merrow, &
Vetter (2012), and from The Worldwide Experimental Platform (theWeP, n.d.).

**\(\mu\)MCTQ** functions were created following the guidelines in Ghotbi
et al. (2020), in addition to the guidelines used for the standard MCTQ.

**MCTQ\(^{Shift}\)** functions were created following the
guidelines in Juda, Vetter, & Roenneberg (2013), in addition to the
guidelines used for the standard MCTQ.

See the References section to learn more.

### Class requirements

The `mctq`

package works with a set of object classes specially created to
hold time values. These classes can be found in the
lubridate and hms
packages. Please refer to those package documentations to learn more about
them.

### Rounding and fractional time

Some operations may produce an output with fractional time (e.g.,
`"19538.3828571429s (~5.43 hours)"`

, `01:15:44.505`

). If you want, you
can round it with `mctq:::round_time()`

.

Our recommendation is to avoid rounding, but, if you do, make sure that you only round your values after all computations are done. That way you avoid round-off errors.

## Operation

The shift version of the MCTQ was developed for shift-workers rotating
through morning-, evening-, and night-shifts, but it also allows adaptations
to other shift schedules (Juda, Vetter, & Roenneberg, 2013). For this reason,
`sjl_weighted()`

must operate with any shift combination.

Considering the requirement above, `sjl_weighted()`

was developed to only
accept `list`

objects as arguments. For this approach to
work, both `sjl`

and `n_w`

arguments must be lists with paired elements and
values, i.e., the first element of `sjl`

(e.g., `sjl_m`

) must be paired with
the first element of `n_w`

(e.g., `n_w_m`

). The function will do the work of
combining them and output a weighted mean.

## Guidelines

Juda, Vetter, & Roenneberg (2013) and The Worldwide Experimental Platform
(n.d.) guidelines for `sjl_weighted()`

(\(\emptyset
SJL_{weighted}\)) computation are as follows.

### Notes

The absolute social jetlag across all shifts (\(\emptyset SJL_{weighted}\)) is the weighted average of all absolute social jetlags.

The authors describe an equation for a three-shift schedule, but this may not be your case. That's why this function works a little bit differently (see the Operation section), allowing you to compute a weighted average with any shift combination.

If you are visualizing this documentation in plain text, you may have some trouble understanding the equations. You can see this documentation on the package website.

### Computation

$$\emptyset SJL_{weighted} = \frac{(| SJL^{M} | \times n_{W}^{M}) + (| SJL^{E} | \times n_{W}^{E}) + (| SJL^{N} | \times n_{W}^{N})}{n_{W}^{M} + n_{W}^{E} + n_{W}^{N}}$$

Where:

\(\emptyset SJL_{weighted}\) = Absolute social jetlag across all shifts.

\(SJL^{M/E/N}\) = Absolute social jetlag in each shift.

\(n_{W}^{M/E/N}\) = Number of days worked in each shift within a shift cycle.

***** \(W\) = Workdays; \(F\) = Work-free days, \(M\) =
Morning shift; \(E\) = Evening shift; \(N\) = Night shift.

## References

Ghotbi, N., Pilz, L. K., Winnebeck, E. C., Vetter, C., Zerbini, G., Lenssen,
D., Frighetto, G., Salamanca, M., Costa, R., Montagnese, S., & Roenneberg, T.
(2020). The \(\mu\)MCTQ: an ultra-short version of the Munich ChronoType
Questionnaire. *Journal of Biological Rhythms*, *35*(1), 98-110.
doi:10.1177/0748730419886986

Juda, M., Vetter, C., & Roenneberg, T. (2013). The Munich ChronoType
Questionnaire for shift-workers (MCTQ\(^{Shift}\)). *Journal of
Biological Rhythms*, *28*(2), 130-140. doi:10.1177/0748730412475041

Roenneberg T., Allebrandt K. V., Merrow M., & Vetter C. (2012). Social jetlag
and obesity. *Current Biology*, *22*(10), 939-43.
doi:10.1016/j.cub.2012.03.038

Roenneberg, T., Wirz-Justice, A., & Merrow, M. (2003). Life between clocks:
daily temporal patterns of human chronotypes. *Journal of Biological
Rhythms*, *18*(1), 80-90. doi:10.1177/0748730402239679

The Worldwide Experimental Platform (n.d.). MCTQ. https://www.thewep.org/documentations/mctq/

## Examples

```
## Scalar example
sjl <- list(sjl_m = lubridate::dhours(1.25),
sjl_e = lubridate::dhours(0.5),
sjl_n = lubridate::dhours(3))
n_w <- list(n_w_m = 3, n_w_e = 1, n_w_n = 4)
sjl_weighted(sjl, n_w)
#> [1] "7312.5s (~2.03 hours)"
#> [1] "7312.5s (~2.03 hours)" # Expected
sjl <- list(sjl_m = lubridate::dhours(1.25),
sjl_e = lubridate::as.duration(NA),
sjl_n = lubridate::dhours(3))
n_w <- list(n_w_m = 3, n_w_e = 1, n_w_n = 4)
sjl_weighted(sjl, n_w)
#> [1] NA
#> [1] NA # Expected
## Vector example
sjl <- list(sjl_m = c(lubridate::dhours(2), lubridate::dhours(2.45)),
sjl_e = c(lubridate::dhours(3.21), lubridate::as.duration(NA)),
sjl_n = c(lubridate::dhours(1.2), lubridate::dhours(5.32)))
n_w <- list(n_w_m = c(1, 3), n_w_e = c(4, 1), n_w_n = c(3, 3))
sjl_weighted(sjl, n_w)
#> [1] "8298s (~2.31 hours)" NA
#> [1] "8298s (~2.31 hours)" NA # Expected
## Checking the first output from vector example
if (requireNamespace("stats", quietly = TRUE)) {
i <- 1
x <- c(sjl[["sjl_m"]][i], sjl[["sjl_e"]][i], sjl[["sjl_n"]][i])
w <- c(n_w[["n_w_m"]][i], n_w[["n_w_e"]][i], n_w[["n_w_n"]][i])
lubridate::as.duration(stats::weighted.mean(x, w))
}
#> [1] "8298s (~2.31 hours)"
#> [1] "8298s (~2.31 hours)" # Expected
## Converting the output to hms
sjl <- list(sjl_m = lubridate::dhours(0.25),
sjl_e = lubridate::dhours(1.2),
sjl_n = lubridate::dhours(4.32))
n_w <- list(n_w_m = 4, n_w_e = 2, n_w_n = 1)
sjl_weighted(sjl, n_w)
#> [1] "3970.28571428571s (~1.1 hours)"
#> [1] "3970.28571428571s (~1.1 hours)" # Expected
hms::as_hms(as.numeric(sjl_weighted(sjl, n_w)))
#> 01:06:10.285714
#> 01:06:10.285714 # Expected
## Rounding the output at the seconds level
mctq:::round_time(sjl_weighted(sjl, n_w))
#> [1] "3970s (~1.1 hours)"
#> [1] "3970s (~1.1 hours)" # Expected
mctq:::round_time(hms::as_hms(as.numeric(sjl_weighted(sjl, n_w))))
#> 01:06:10
#> 01:06:10 # Expected
```