Overview of the dataset

The Chicago Crime Data 2016-2021 includes 1500378 valid data crime records that happened in Chicago area during 2016-01-01 to 2022-02-01. To maintain the balance of the year round, the data of the first two months in 2022 were discarded. After dropping useless columns such as 'x_coordinate' and 'id', a data subset which contains 1476415 valid records and 12 columns are kept.

date block primary_type description arrest domestic district community_area updated_on location_description latitude longitude
2016-05-03 09:45:00 055XX W VAN BUREN ST ASSAULT AGGRAVATED-HANDGUN False False 15 25 2020-03-25 15:45:43 STREET 41.874758 -87.762379
2016-05-19 00:00:00 026XX W NORTH AVE BATTERY AGGRAVATED-HANDGUN False False 14 24 2020-03-25 15:45:43 STREET 41.910261 -87.692759
2016-05-22 21:25:00 057XX W BLOOMINGDALE AVE BATTERY AGGRAVATED-HANDGUN False False 25 25 2020-03-25 15:45:43 PARK PROPERTY 41.912628 -87.768864
2016-06-01 01:22:00 013XX W LELAND AVE BATTERY AGGRAVATED-HANDGUN False False 19 3 2020-03-25 15:45:43 SIDEWALK 41.967145 -87.663292
2016-06-10 15:00:00 007XX S HOMAN AVE ASSAULT AGGRAVATED-HANDGUN False False 11 27 2020-03-25 15:45:43 STREET 41.872253 -87.710733
... ... ... ... ... ... ... ... ... ... ...

Data Source: Chicago Data Portal.

Timing Analysis

Which Crime Types are the Commonest?

Figure-1 serves to check the relative number of different crime cases during these years. To make the short bars more legible, a log-y axis is applied. A range slide bar is added to the bottom to help switch the year. Bars are partly arranged decreasingly to keep the orders and enhance reading experience. Blue-red colorscale is applied to highlight the most common crime types.

During 2016-2021, the commonest top5 crime types are:

  • Theft
  • Battery
  • Criminal Damage
  • Deceptive Practice
  • Assault

    • Figure 1. Yearly crimes count by types
    (You can drag the slider)




    Figure 2. Daily crime cases in Chicago 2016 - 2021

    What is the crime cases change pattern in the last six years in Chicago?

    The interactive calendar plot Figure-2 serves to present the daily crime cases during 2016 - 2021. The trend and yearly pattern of the past 6 years can be easily found on the heatmap. Checking a certain day's crime cases can be easily done by clicking on the specific date.

    Judging from Figure-2, some patterns are revealed:

  • The daily crime cases are much more in summer than in winter. This could be explained by weather conditions. Chicago's extremely cold winter may cause a decrease in the number of the homeless, thus decreasing the crime cases.
  • An all-year-round decrease of the crime cases started at the beginning of the 2020. This pattern could be associated with the COVID-19 pandemic. Many citizens started to work from home and tried to avoid unnecessary going out.
  • In 2021, the crimes increased, compared with 2020. Citizens gradually returned to normal life, leading the crime rate slowly back to its original level.
  • The crime number of 2020/5/31 is especially high. This extreme case was associated with the notorious violent crime - the single most violent day in Chicago in six decades. 18 people were murdered in Chicago on May 31. news link

    • Any suggestions for the citizens of Chicago?

  • With the alleviation of the epidemic, citizens of Chicago should pay more attention to the potential crimes, especially in summer.



    • When does the crime usually happen in a day?

    It is widely accepted that crimes are more likely to happen during the night. Accordingly, to figure out if it is the truth, Figure-3, a clock-shaped radar chart was plotted with a dropdown menu, so that you can pick up different types of crime to analyze the detailed shape of the hourly distribution of crime cases.

    Crimes happening mostly during the night (18:00 - 6:00):

  • Battery
  • Criminal Damage
  • Robbery
  • Motor Vehicle Theft
  • Weapons Violation

    • Crimes happening mostly during the day (6:00 - 18:00):

  • Theft
  • Assault
  • Deceptive Practice
  • Narcotics
  • Burglary

    • Figure 3. Chicago crime hourly distribution
    (You can select on the dropdown menu)

    Geographical Analysis

    Which community is the most dangerous and which is the most safe community in Chicago?

    The Crime Count Choropleth Map aims to show user a overview on the crime distribution. It uses a color hue to indicate the number of crimes in each communities in Chicago. The darker the color, the higher the number of crimes is. The hover labels show the name and number of crimes of the community. Below the plot is the slider, helping to show the changes of the crime through the years.

    Based on the choropleth map, the most dangerous communities are:

  • Austin
  • Near North Side
  • Midtown areas

    • The safest communities are:

  • Hegewisch
  • Burnside
  • Edison Park
  • Montclare

    • Figure 4. Chicago yearly crime count community map




    Figure 5. Chicago yearly crime count block map

    Where does the crime tend to happen?

    This map provides a crime density plot on a block basis. To zoom in the map, you can get an idea on the frequency of the crime happened in this block, by looking at the color. If the color is red, that means this block has a high frequency of crimes and if the color is blue or even hard to see, that means crimes do not happen here frequently.

    There are a lot of crimes happened in downtown Chicago. South central area is also a place that crimes usually happen as well as the shore area in Chicago.

    In more details, most of the crimes clustered at the crossroads and corners of the blocks.

    Subtypes Analysis

    What are the most common crime types?

    To reveal all the crime types and the proportion of each type, we create a sunburst plot on the right. In agreement with the plot, all the 1.5M records of crime can be divided into over 20 primary types, in which the type of THEFT takes the largest proportion. Within the primary types, each crime case was matched with a detailed description. To interact with the plot, you can click on each primary type to dig deep into it and learn more about the subtypes, and clicking on the internal circle can take you back to the previous level.

    Based on the plots, the Top 10 primary crime types are as follows:

  • Theft
  • Battery
  • Criminal Damage
  • Assault
  • Robbery
  • Deceptive Practice
  • Narcotics
  • Motor Vehicle Theft
  • Burglary
  • Weapons Violation

    • Figure 6. Chicago crime subtype sunburst plot




    The Arrested and Domestic Case by Crime Types

    This interactive treemap serves to check the number of arrested and unarrested cases as well as the portion of different crime types within. Some minority crime types are merged as 'Other Types' to make them legible. The hierarchical structure is 'Arrest-Crime Type-Domestic', which helps the reader check more easily what crime types have more arrested cases and what does not. As a functionality of plotly treemap, the reader can click and open every block for detailed information.

    What calls for attention?

  • Most crimes were not arrested, the arrested ratio is roughly 4:1.
  • Narcotics are the 1st reason for arrest. All of them are non-domestics.
  • Battery are the 2nd reason for arrest, half of them related with family issue.

    • Figure 7. Case count by arrest, crime type and domestic




    We have another treemap serving to check the arrested-unarrested ratio of each crime types and their relative case numbers. The hierarchical structure is 'Crime Type-Arrest-Domestic'. Each crime types is colored uiquely to enhance reading experience.

    What calls for attention?

  • Theft and battery are the two most common crime types, but most of the cases are unarrested.
  • It seems tht narcotics is the only 100% arrested crime type.
  • Other violent crime types, such as assault, burglary and robbery, have very low arrest portion.
  • Battery is a crime type that has close numbers of domestic and non-domestic cases. Either type got half arrested.

    • Figure 8. Cause count by crime type, arrest and domestic

    Conclusion

    Crimes number in Chicago

  • During 2016-2019, the yearly number of crime cases in Chicago kept decreasing. After 2020, due to the Covid 19 impact, the number of crime cases in Chicago dropped drastically. Generally, Chicago is getting better.
  • Among the recorded crime types, theft and battery have the most cases in any year. These 2 crime types take around 40 percentage of all cases in Chicago.
  • Although numerous cases happen daily in Chicago, there are less than 20 percent of the cases got the criminal arrested.

    • Happend when and where?

  • Except 2020 and 2021, which has balanced number of crime cases across the year, in ordinary years, there are more crime cases between May and October. It is intuitive that warmer weather is beneficial for crimes as there is higher people turnover.
  • According to the statistical work, common crimes such as theft and assault are more likely to happen in the afternoon and the evening. However, there are also some crimes like robbery, which has higher chance to happen during the midnight.
  • Crimes are more likely to happen in the environment which has complex transportation or building layout. Crossroads and corners of blocks are highly risky places where unexpected crimes could take place.
  • The north area has relatively better public security. Most of cases happened in Chicago downtown and some communities in the south area.

    • Safety guides for individuals

  • Aviod hanging out alone in unfamiliar places. Stay with crowd, stay with friends. Be aware of the nearest places to find help such as police station or school security bureau. When in emergency, do not hesistate to call 911.
  • Even faced with domestic crimes, you can resort to 911 for help. They are even tougher for domestic crimes.
  • Aviod going out in late time. Although many crimes happen during daytime, it is very hard to get support during night time.
  • Stay away from blocks in poor security condition. Stay away from places where tramp and drug addicts gathered. In Chicago, downtown and south area has more crime records than the north area.



    • Check the code of the visualization.