Assignment

Trends in Crimes Change over Weekdays and Hours of the Day

The following is an analysis of a subset of crime data obtained from June 1 to August 31, 2014.

Figure 1 shows total number of crimes over the 24 hours of the day. The crimes within each hour were summed up. The figure (1) shows total number of crimes committed on each day of the week, (2) separates weekdays (solid lines) and weekends (dashed lines), and (3) shows means taken over weedays (solid black line) and weekend days (dashed black line).

There are three important things to take away from the figure. First, there is a general trend for crime rates to increase over the course of the day, with least crimes occurring at 5 AM, and most crimes occurring at midnight. Second, there is a spike in crimes that occurs around lunchtime, at noon. Third, the crime trends on weekends are shifted over for a part of the day, such that the post-midnight decline in crimes is slower on the weekends than on the weekdays, and the increase leading up to noon is also slower. This is likely due to more people being out on the weekends and thus more crimes are reported late at night. People are also more likely to sleep in on the weekends, which could account for the slower increase in the morning. However, both weekends and weekdays showed a spike in crime rates around lunch time, and following lunch the two rates were roughly the same.

Figure 1. Crimes reported over the course of the day.

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Figure 2 shows that the daily pattern is different for different crimes. The figure shows 7 most common crimes (>1,000 crimes over the course of the summer). Most notably, the noon spike is most evident for non-vehicle theft, burglary, and fraud. The increase over the course of the day is most evident for theft (vehicle and non-vehicle). Assault & threads and property damage also show increases throughout the day although not as steep.

Figure 2. Daily trends over different types of crimes.

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In Figure 3 we see trends in crime rates over weekdays for different types of crime. The most important finding is that different crimes tend to peak on different days. Most notably, non-vehicle thefts tend to peak on Fridays, Saturday, and Sundays, whereas burglary is high on Friday, but lower on the days of the weekend.

Figure 3. Number of different types of crimes by day of week.

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