aoristic.df {aoristic}

Calculate aoristic weights

Description

Calculates aoristic proportional weights across 168 units representing each hour of the week (24 hours x 7 days). It is designed for situations when an event time is not know but could be spread across numerous hours or days, and is represented by a Start (or From) date and time, and an End (or To) date and time. The output retains the source data, and can be reimported into a GIS for spatial analysis. The output from this function is used in other aoristic library functions.

Usage

aoristic.df(data1, Xcoord, Ycoord, DateTimeFrom, DateTimeTo)

Arguments

data1

data frame with a minimum of 4 columns with X, Y coords, Start and End date/time

Xcoord

a vector of the event X coordinate or latitude (numeric object)

Ycoord

a vector of the event Y coordinate or longitude (numeric object)

DateTimeFrom

a vector of the column name for FromDateTime (POSIXct date-time object)

DateTimeTo

a vector of the column name for ToDateTime (POSIXct date-time object)

Details

NOTE: If an observation is missing the End/To datetime, the entire aoristic weight (1.0) will be assigned to the hour block containing the Start/From datetime. Events with start datetime events after the end datetime will also be assigned to the hour block containing the Start/From datetime. Events with time spans lasting more than one week (>168 hours) will default to a time span of 168 hours and a value of ~ 0.0059 (1/168) assigned to each day/hour.

Value

A data frame with aoristic values for each hour of the week for each observation

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.

Examples

df <- aoristic.df(dcburglaries, 'X', 'Y', 'StartDateTime', 'EndDateTime')