Analyzing violent crime, workflow

Workflow using ArcGIS Online

Note:

The steps below are based on the March 2016 update of ArcGIS Online, but should work fine for later software releases as well. You may notice slight differences in the maps below if you are using a more current version of ArcGIS Online, the result of an improvement in how points are positioned within the fishnet grid of Find Hot Spots. You will need Administrator privileges in order to perform the analyses outlined below. Keep in mind that storing and analyzing data consumes credits.

Get the data for the analysis.

1. Sign in to your ArcGIS Online account.
2. Search for CrimeAnalysisData. When it displays, select Add layer to new map.



Note:

The default search is within your organization. If you aren't finding the data, ensure this default is unchecked.

You will likely see a message indicating the layer did not draw completely. Ignore this message. While not all crime events will draw, your analyses below will apply to all of the data.

Create a hot spot map of violent crime densities.

1. Hover over the Violent Crime 2014 layer and click the perform analysis button . Select Analyze Patterns and the Find Hot Spots tool.
2. Specify that you want to Find clusters of high and low Point Counts, to Count points within a Fishnet Grid and to use the Analysis Boundary layer to Define where points are possible. In addition, provide a Result layer name such as ViolentCrimeHotSpots. You may want to click Show credits to see how many credits will be consumed before you run the analysis.





2014 violent crime hot spots.

Hot spot with 99 percent confidence	Cold spot with 90 percent confidence
Hot spot with 95 percent confidence	Cold spot with 95 percent confidence
Hot spot with 90 percent confidence	Cold spot with 99 percent confidence
Not statistically significant

Create a hot spot map of liquor vendors to compare to the violent crime hot spot map.

1. Hover over the Liquor Vendors layer and click the perform analysis button . Again, select Analyze Patterns and the Find Hot Spots tool.
2. To make sure this new hot spot map lines up with the previous one, use the Violent Crime Hot Spots result layer for the Count points within parameter. Also specify a Result layer name such as LiquorVendorHotSpots. You may want to click Show credits to see how many credits will be consumed before running the analysis.



Now you can visually compare the hot spot maps to see where their activity spaces overlap.



Violent crime hot spots versus liquor vendor hot spots.

Hot spot with 99 percent confidence	Cold spot with 90 percent confidence
Hot spot with 95 percent confidence	Cold spot with 95 percent confidence
Hot spot with 90 percent confidence	Cold spot with 99 percent confidence
Not statistically significant

Caution:

If you are zoomed in so only a portion of the study area is displayed, be sure to either zoom back out until you see the entire study area or uncheck the Use current map extent parameter prior to running your analyses. When the Use current map extent is checked, only the areas being displayed are analyzed.

Get poverty data for each of the polygon grids in the violent crime hot spot analysis layer.

The Enrich Layer tool always provides the most current data available. Your results may look different below if you are using more current data. The field for Households with Income Below Poverty Level might be for 2010-2014, for example, or it may be even more current.

1. Hover over the ViolentCrimeHotSpots layer and click the perform analysis button . Click Data Enrichment and select the Enrich Layer tool.
2. Click the Select Variables button to see the variable categories. Select Poverty, click on Households with Income Below Poverty Level, and click Apply. Provide a name, such as PovertyData, for the result layer. Uncheck Use current map extent. You may want to check how many credits will be consumed prior to running the analysis.



The new layer with the data you selected is added to the map. You may see a message indicating the layer didn't draw completely, but be assured, you did receive data for the entire study area.

Tip:

Each time you run the Enrich Layer tool, you use ArcGIS Online credits (even when you run the tool in ArcGIS Pro). You may want to create the data once and use it in other applications. If you create the data using the Enrich Layer tool in ArcGIS Pro, for example, you can publish it to your ArcGIS Online account as follows:

• In ArcGIS Pro, right-click the layer and select Share As Web Layer.
• On the Share Web Layer panel, indicate you want to publish Features. Fill out the Summary and Tags parameters. Click the Publish button.

The layer will appear in your ArcGIS Online account My Content.

Create a hot spot map of poverty.

1. Hover over the PovertyData layer and click the perform analysis button again. Select Analyze Patterns and the Find Hot Spots tool.
2. Set the Find clusters of high and low parameter to the variable for households with incomes below the poverty level. Specify an output results layer name, such as PovertyHotSpots, and run the analysis. Uncheck Use current map extent.





Hot spots of poverty.

Hot spot with 99 percent confidence	Cold spot with 90 percent confidence
Hot spot with 95 percent confidence	Cold spot with 95 percent confidence
Hot spot with 90 percent confidence	Cold spot with 99 percent confidence
Not statistically significant

Overlay the violent crime, liquor vendor, and poverty hot spot maps to find where they overlap.

1. Begin by selecting the features of interest. For the violent crime hot spots, liquor vendor hot spots, and poverty hot spots, filter only those locations where the Gi_Bin Fixed 4554_FDR field is 3 (this is the code for statistically significant hot spots at the 99 percent confidence level). To bring up the Filter panel, hover over a layer to reveal the action buttons and click filter .





The most intense violent crime, liquor vendor, and poverty hot spots.

Dive-in:

Why such an odd field name? The Find Hot Spots tool runs the Gi* statistic. The z-score results are binned (Gi_Bin) by statistical significance levels: 90, 95, or 99 percent. The scale of analysis is a fixed distance; in this case the fixed distance is 4554 feet (FIXED 4554). An FDR correction was applied to increase reliability of the results. If you click the drop-down box next to the result layer and select Show Item Details, you will see more information about the statistical parameters applied to your analysis. A number of resources provide more information about hot spot analysis and the Gi* statistic.

2. Next, use the Overlay Layers tool to find the intersection among all of the filtered hot spot maps. Hover over the violent crimes hot spot layer then click the perform analysis button . Select Manage Data and the Overlay Layers tool. Specify the liquor vendor hot spot layer for the Choose overlay layer parameter, provide a result name such as iCrimeLiquor, and run the analysis.
3. Finally, hover over the output from the first overlay operation and click the perform analysis button . Select Manage Data and the Overlay Layers tool as you did before. Specify the poverty hot spot layer for the Choose overlay layer parameter, and run the tool again. The resulting output layer is the overlap among all three of the filtered hot spot maps.



Note:

Your map may look a bit different if you are using more current poverty data. In fact, you may not have any areas that overlap for crime, liquor vendor and poverty hot spots.



Areas where violent crime, liquor vendor, and poverty hot spots overlap.

You will recommend the overlap areas in the map above for remediation efforts aimed at limiting access to alcohol.

Analyze violent crime trends.

The space-time pattern mining tools are not currently available in ArcGIS Online but you can create the crime trend map you need using ArcMap or using ArcGIS Pro. You can then publish the results to your ArcGIS Online account. Once the crime trend map has been published, you can add it to your map from your My Content. Alternatively, use the ViolentCrimeTrends and ViolentCrimeTrendsMap services that have already been created for you.

1. To use the services that have already been created for you, follow the steps below. If you publish your own crime trend map using ArcMap or using ArcGIS Pro, you can use these same steps to add your published services to your ArcGIS Online map.
   1. Click Add Content to Map, and Search for Layers.

      

   2. Find ViolentCrimeTrend* in ArcGIS Online within the map area and add both the feature service and the map service. Exit the Search for Layers pane by clicking on Done Adding Layers.

      

   3. Examine ViolentCrimeTrendsMap and the trend categories identified.

      

      2014 violent crime trends.

2. To publish the crime trend map from ArcGIS Pro, follow the steps below.
   1. In ArcGIS Pro, right-click the violent crime trends layer and select Share As Web Layer.
   2. On the Share Web Layer panel, indicate you want to publish Features. Fill out the Summary and Tags parameters, and click the Publish button. The crime trends map will appear in your ArcGIS Online account My Content.
   3. The symbology for the features will not be correct, but you can also publish the layer as a map service by repeating the steps above and checking Tiles (instead of Features). You will still need the actual features for analysis.

      

   4. Add the crime trend layer to your ArcGIS Online map using the same approach outlined in step one.
3. Publish the crime trend map from ArcMap.
   1. Right-click on the violent crime trends layer and select Save As Layer File. This creates a LYR file with the layer symbology.
   2. Open a new blank ArcMap document (.mxd) and add the new LYR file .
   3. If necessary, sign in to your ArcGIS Online account.
   4. From the File tab, select Share As and select Service.

      

   5. Select Publish a Service and click Next.
   6. Choose the connection and provide a service name, such as ViolentCrimeTrends. Click Continue.
   7. From the list of options along the left side of the dialog box, select Capabilities and check Feature Access.

      

      .
   8. For the Item Description, provide a summary, tags, and description.
   9. In the upper right corner of the dialog box, click Publish.
   10. The symbology for the features will not be correct, but you can also publish the layer as a map service by repeating the steps above and checking Tiled Mapping (instead of Feature Access). You will still need the actual features for analysis.
   11. Add the crime trend layer to your ArcGIS Online map using the same approach outlined in step one.

Get the unemployment rate data matching the violent crime trends geometry.

Note:

The Enrich Layer tool always provides the most current data available. Your results may look different below if you are using more current data. The field for Unemployment Rate, for example, may be 2016 or even more current.

1. Hover over the ViolentCrimeTrends feature layer and click the Perform Analysis button, .
2. Click Data Enrichment and select the Enrich Layer tool.
3. Click the Select Variables button to see the variable categories. Select Jobs and click Unemployment Rate and Apply. Provide a name, such as UnemploymentData, for the result layer. Uncheck Use current map extent. You may want to check how many credits will be consumed. Click the Run Analysis button.



The new layer with the data you selected is added to the map. You may see a message indicating the layer didn't draw completely, but you did receive data for the entire study area.

Create a hot spot map of the unemployment rate data.

1. Hover over the unemployment rate data layer you obtained using the Enrich Layer tool and click the perform analysis button . Select Analyze Patterns and the Find Hot Spots tool.
2. Set the Find clusters of high and low parameter to the unemployment rate variable. Specify an output results layer name, such as UnemploymentHotSpots, uncheck Use current map extent, and run the analysis.



2015 unemployment rate hot spots.

Hot spot with 99 percent confidence	Cold spot with 90 percent confidence
Hot spot with 95 percent confidence	Cold spot with 95 percent confidence
Hot spot with 90 percent confidence	Cold spot with 99 percent confidence
Not statistically significant

Now you are ready to overlay the crime trends map with the unemployment hot spot map.

1. Select the features of interest using a filter. To bring up the Filter panel, hover over the unemployment hot spot map to reveal the action buttons, then click the filter button . Add an expression to select locations where the Gi_Bin Fixed 4554_FDR field is 3 (this is the code for statistically significant hot spots at the 99 percent confidence level).



2. For the crime trends map, you are interested in specific Pattern Type values: Intensifying, Consecutive, and Persistent hot spots. Hover over the crime trends layer and click the filter button . Add each expression below. Be sure Display features in the layer that match is set to Any.
   • PATTERN is Consecutive Hot Spot
   • PATTERN is Intensifying Hot Spot
   • PATTERN is Persistent Hot Spot



3. Finally, overlay the filtered layers. Hover over the violent crime trends layer and click the perform analysis button . Select Manage Data and the Overlay Layers tool. Select your filtered unemployment hot spot map for the Choose overlay layer parameter. Provide a name for the result layer, such as iCrimeUnemp, and run the analysis.

Note:

Your map may look a bit different if you are using more current unemployment rate data.



Remediation areas where persistent, intensifying, and consecutive violent crime hot spots overlap with high unemployment rates.

Lastly, select the high schools falling within a quarter mile of the proposed remediation areas.

1. Hover over the Public High Schools layer and click the perform analysis button . Select Find Locations. Click on the Find Existing Locations tool.
2. Add the expression to find public high schools within 0.25 miles of the crime and unemployment overlap areas.



3. Specify a name for the result layer, such as SelectedHighSchools, and run the analysis.
Note: your results will look a bit different if you are using more current data.



High schools for consideration in an expanded summer jobs program.

Note:

Whenever you want to change the colors or symbols on your map, hover over the layer you want to modify and select the Change Style button .

You are now ready to make your final recommendations.

• Analyzing violent crime - analysis overview
• References and resources for learning more