|London police violent and acqusitive crime incident in 2009 numbers each day|
I have carried out a simple analysis to test three important aspects of my research;
- How good is the SPSS 17 k means classification method
- Does the Metropolitan Police Service CAD data contain rhythms and cycles that reflect the lives of the people of London and the way it is policed.
- What is the best CAD data to use to detect these rhythms and cycles.
I carried out a k means classification using those four variables with the 365 days of the year as cases (using raw unstandardised data). I asked for seven groups to see if the k means classification could split the days into the right weekdays.
I find the result shown in the graph above quite exciting. I hope you can see why. The classification recognises a clear difference between Saturdays and Sundays and week days. The week days have been subdivided in two groups. I have been through all the dates which appear to have allocated to the wrong group and there is a very good explanation for each. For instance each Monday that was allocated to the typically Sunday group (group1) were Bank Holiday Mondays. Every other "misallocation" had a weather or holiday related explanation.
I have tried the classification with standardised data and additional and fewer variables but these four variables appear to me to produce the best results.
So I now have even more confidence in the k means classification method, I am convinced I using a good set of data and I am sure that analysing the variations in violent and acquisitive crime incidents in the context of the police response is worthwhile.