crime risk forecasting: near repeat pattern analysis & load forecasting
DESCRIPTION
http://www.azavea.com/hunchlab This is a rather technical dive into the near repeat pattern analysis and load forecasting features that we've built into HunchLab. Both of these features are aimed at helping a law enforcement agency to better predict risk levels across their jurisdictions and allocate resources according. While no application of predictive analytics will be perfect, forecasting risk based on models of the past can help officers and analysts to anticipate the appropriate next steps. Near repeat pattern analysis helps officers quantify the risk that arises from multiple incidents happening close to one another in space and time. What we are quantifying is how the fact that your neighbor's house is burgled raises your risk of a burglary in the coming days and weeks. With load forecasting we are looking at cyclical temporal patterns in incidents. How does the time of year, time of day, and day of week change the levels of crime incidents that we should expect across a jurisdiction? By modeling these cyclical patterns we can project crime levels into the future, helping law enforcement agencies to allocate resources appropriately as well as better manage organizational accountability.TRANSCRIPT
340 N 12th St, Suite 402Philadelphia, PA 19107
www.azavea.com/hunchlab
Crime Risk Forecasting
Near Repeat Pattern Analysis and Load Forecasting
About Us
Robert CheethamPresident & [email protected]
Jeremy HeffnerHunchLab Product [email protected]
Agenda
• Company Background• HunchLab
– Risk Forecasting• Near Repeat Pattern Analysis• Load Forecasting
– Future Research Topics
• Q&A
About Azavea
• Founded in 2000
• 25 people
• Based in Philadelphia
– Boston satellite office
• Geospatial + web + mobile
– Software development
– Spatial analysis services
Clients & Industries
• Public Safety• Municipal Services• Public Health• Human Services• Culture • Elections & Politics• Land Conservation• Economic Development
Azavea & Governments
HunchLab
web-based crime analysis, early warning, and risk forecasting
Crime Analysis
– Mapping (spatial / temporal densities)
– Trending
– Intelligence Dashboard
Early Warning
– Statistical & Threshold-based Hunches (data mining)
– Alerting
Risk Forecasting
– Near Repeat Pattern
– Load Forecasting
Near Repeat Pattern Analysis
Contagious Crime?
• Near repeat pattern analysis • “If one burglary occurs, how does the risk change nearby?”
What Do We Mean By Near Repeat?
• Repeat victimization– Incident at the same location at a later time (likely
related)
• Near repeat victimization– Incident at a nearby location at a later time (likely
related)
• Incident A (place, time) --> Incident B (place, time)
Near Repeat Pattern Analysis
• The goal:– Quantify short term risk due to near-repeat victimization
• “If one burglary occurs, how does the risk of burglary for the neighbors change?”
• What we know:– Incident A (place, time) --> Incident B (place, time)
• Distance between A and B• Timeframe between A and B
• What we need to know:– What distances/timeframes are not simply random?
Near Repeat Pattern Analysis
• The process– Observe the pattern in historic data– Simulate the pattern in randomized historic data– Compare the observed pattern to the simulated patterns– Apply the non-random pattern to new incidents
• An example– 180 days of burglaries in Division 6 of Philadelphia
Near Repeat Pattern Analysis
Near Repeat Pattern Analysis
Near Repeat Pattern Analysis
Near Repeat Pattern Analysis
Near Repeat Pattern Analysis
• How can you test your own data?– Near Repeat Calculator
• http://www.temple.edu/cj/misc/nr/
• Papers– Near-Repeat Patterns in Philadelphia Shootings (2008)
• One city block & two weeks after one shooting– 33% increase in likelihood of a second event
Jerry RatcliffeTemple University
Demo
Load Forecasting
Improving CompStat
• Load forecasting• “Given the time of year, day of week, time of day and
general trend, what counts of crimes should I expect?”
What Do We Mean By Load Forecasting?
• Load forecasting• Generating aggregate crime counts for a future timeframe
using cyclical time series analysis
Measure cyclical patterns
Identify non-cyclical trend
Forecast expected count
+
bit.ly/gorrcrimeforecastingpaper
Load Forecasting
• Measure cyclical patterns• Take historic incidents (for example: last five years)• Generate multiplicative seasonal indices
– For each time cycle:» time of year» day of week» time of day
– Count incidents within each time unit (for example: Monday)– Calculate average per time unit if incidents were evenly
distributed– Divide counts within each time unit by the calculated average
to generate multiplicative indices» Index ~ 1 means at the average» Index > 1 means above average» Index < 1 means below average
Load Forecasting
Load Forecasting
Load Forecasting
Load Forecasting
Load Forecasting
• Identify non-cyclical trend• Take recent daily counts (for example: last year daily
counts)• Remove cyclical trends by dividing by indices
• Run a trending function on the new counts– Simple average
» Last X Days
– Smoothing function» Exponential smoothing» Holt’s linear exponential smoothing
Load Forecasting
• Forecast expected count• Project trend into future timeframe
– Always flat» Simple average» Exponential smoothing
– Linear trend» Holt’s linear exponential smoothing
• Multiple by seasonal indices to reseasonalize the data
Load Forecasting
Measure cyclical patterns
Identify non-cyclical trend
Forecast expected count
+
bit.ly/gorrcrimeforecastingpaper
How Do We Know It’s Accurate?
• Testing• Generated forecasting packages (examples)
– Commonly Used» Average of last 30 days» Average of last 365 days» Last year’s count for the same time period
– Advanced Combinations» Different cyclical indices (example: day of year vs. month of year)» Different levels of geographic aggregation for indices» Different trending functions
• Scoring methodologies (examples)– Mean absolute percent error (with some enhancements)– Mean percent error– Mean squared error
• Run thousands of forecasts through testing framework• Choose the right technique in the right situation
Demo
Research Topics
Research Topics
• Analysis– Real-time Functionality
• Consume real-time data streams• Conduct ongoing, automated analysis• Push real-time alerts
• Risk Forecasting– Load forecasting enhancements
• Machine learning-based model selection• Weather and special events
– Combining short and long term risk forecasts• NIJ project with Jerry Ratcliffe & Ralph Taylor• Neighborhood composition modeling using ACS data
– Risk Terrain Modeling
Research Topics
• Current Implementation Funding– Local Byrne Memorial JAG solicitation due July 21, 2011
• http://www.ojp.usdoj.gov/BJA/grant/jag.html
• Research Funding
Q&A
Contact Us
Robert CheethamPresident & [email protected]
Jeremy HeffnerHunchLab Product [email protected]