activity (version 1.3)

transtime: Transforms clock time to solar times.

Description

Transforms time expressed relative to either the time of a single solar event (anchor times - Nouvellet et al. 2012), or two solar events (such as sun rise and sun set - Vazquez et al. in press).

Usage

transtime(dat, anchor, mnanchor = NULL, type = c("average",
  "equinoctial", "single"))

Arguments

dat

A vector of radian event clock times.

anchor

A vector or matrix matched with dat containing radian anchor times on the day of each event (see Details).

mnanchor

A scalar or two-element vector of numeric radian mean anchor times (see Details).

type

The type of transformation to use (see Details).

Value

A vector of radian transformed times.

Details

If double anchoring is requested (i.e. type is equinoctial or average), the anchor argument requires a two-column matrix, otherwise a vector. The argument mnanchor can usually be left at its default NULL value. In this case, the mean anchors are set to c(pi/2, pi*3/2) when type=="equinoctial", otherwise the anchor mean(s).

Although the anchors for transformation are usually likely to be solar events (e.g. sun rise and/or sunset), they could be other celestial (e.g. lunar) or human-related (e.g. timing of artificial lighting) events.

References

Vazquez, C., Rowcliffe, J.M., Spoelstra, K. and Jansen, P.A. in press. Comparing diel activity patterns of wildlife across latitudes and seasons: time transformation using day length. Methods in Ecology and Evolution.

Nouvellet, P., Rasmussen, G.S.A., Macdonald, D.W. and Courchamp, F. 2012. Noisy clocks and silent sunrises: measurement methods of daily activity pattern. Journal of Zoology 286: 179-184.

Examples

# NOT RUN {
data(BCItime)
subdat <- subset(BCItime, species=="ocelot")
jdate <- insol::JD(strptime(subdat$date, "%d/%m/%Y %H:%M", "UTC"))
suntimes <- pi/12 * insol::daylength(9.156335, -79.847682, jdate, -5)[, -3]
rawtimes <- subdat$time*2*pi
avgtimes <- transtime(rawtimes, suntimes)
eqntimes <- transtime(rawtimes, suntimes, type="equinoctial")
sngtimes <- transtime(rawtimes, suntimes[,1], type="single")
rawAct <- fitact(rawtimes)
avgAct <- fitact(avgtimes)
eqnAct <- fitact(eqntimes)
sngAct <- fitact(sngtimes)
plot(rawAct)
plot(avgAct, add=TRUE, data="n", tline=list(col="magenta"))
plot(eqnAct, add=TRUE, data="n", tline=list(col="orange"))
plot(sngAct, add=TRUE, data="n", tline=list(col="cyan"))
# }