Days of the week

Many crime or disorder reporting systems include a field that codes the day of the week when the event occurred. Those that do not code by the day of the week at least have a date that is entered onto the report, which can have a code for the day of the week extracted from it (e.g. 10/02/2000 was a Thursday). This data can then be aggregated by these days of the week to reveal on which days events peak.

It is also important to consider the date range that may exist in certain crime and disorder records. This is most often the case with property crimes where there is a reported ‘committed from date’ and a ‘committed to date’.

Date range analysis.

A suitable method that incorporates the date range in an analysis of hotspots on days of the week is referred to as the weighted method. The method assigns probabilities to each day within the range that relate to when the incident may have occurred. These probabilities calculated for all incidents are then summed for each day to reveal trends in the change of incidents over the days of the week.

Consider the following crime record examples.

Residential burglary record 1 spans 2 days (Friday 12th January to Saturday 13th January). Record 2 has a range of 10 days. Residential burglary 3 occurred on the 14/01/2001. Probabilities that relate to the day of the week when the burglary occurred can be calculated from these ranges. These probabilities are shown below.

The sum of the individual weights for all crime records is then calculated to reveal how crime changes over the duration of a week.

Analysing the occurrence of residential burglary by days of the week in the London Borough of Croydon (June 1999 to May 2000) revealed that there was a slight peak on Friday’s and that Sunday’s was the quietest day for this crime type (see graph below).

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