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Aoristic weights

Source: R/doss.R
aorwt.Rd

Spreads each event known only to have happened in an interval [from, to) with uniform density over that interval and counts each instant in the bin of its local clock time (Ratcliffe 2002): with the defaults, the 168 hours of the week from Sunday 00:00. A change of clock (daylight saving) moves the remaining time to the right hours: skipped hours get nothing and a repeated hour gets both. Missing values follow stated rules: an event with no from is left out; with no to, a reversed interval or one shorter than lo seconds, its whole weight goes to the start's bin; one of at least hi seconds is spread evenly over all bins.

Usage

aorwt(
  from,
  to,
  bw = 3600,
  nb = 168,
  origin = 259200,
  off = 0,
  tt = NULL,
  toff = NULL,
  lo = 120,
  hi = 604800,
  each = FALSE
)

Arguments

from, to

The start and end of each event's interval: date-times (POSIXct) or seconds since 1970-01-01 UTC; NA allowed as above, not infinite values.

bw

The bin width in seconds, positive.

nb

The number of bins in a period: one whole number from 1.

origin

The local clock time at which bin 1 starts, in the same units (the default is Sunday 1970-01-04 00:00).

off

The offset of the local clock from UTC in seconds, before tt[1] (for a fixed offset, the only one).

tt, toff

NULL, or the instants at which the local clock's offset changes (strictly increasing) and the new offsets.

lo, hi

The lengths in seconds below which an interval counts at its start and from which it counts everywhere, 0 <= lo < hi (lo = 0, hi = Inf spread every interval exactly).

each

TRUE to return each event's weights.

Value

A list: tot (the summed weights by bin), w (NULL, or a matrix with one row per event and one column per bin, rows summing to 1, 0 for events left out) and cnt (events left out, without end, reversed, short and long).

References

Ratcliffe, J. H. (2002). Aoristic signatures and the spatio-temporal analysis of high volume crime patterns. Journal of Quantitative Criminology, 18(1), 23-43. doi:10.1023/A:1013240828824

Examples

f <- as.POSIXct(c("2024-03-04 22:00", "2024-03-05 09:30"), tz = "UTC")
t <- as.POSIXct(c("2024-03-05 02:00", "2024-03-05 10:30"), tz = "UTC")
a <- aorwt(f, t, bw = 3600, nb = 24, origin = 0)
a$tot
#>  [1] 0.25 0.25 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.50 0.50 0.00 0.00 0.00 0.00
#> [16] 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.25 0.25