## Aggregate Points

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This tool works with a layer of point features (the analysis layer) and a layer of area features. It first figures out which points fall within each area. After determining this point-in-area spatial relationship, statistics about all points in the area are calculated and assigned to the area. The most basic statistic is the count of the number of points within the area, but you can get other statistics as well.

For example, suppose you have point features of coffee shop locations and area features of counties, and you want to summarize coffee sales by county. Assuming the coffee shops have a TOTAL_SALES attribute, you can get the sum of all TOTAL_SALES within each county, or the minimum or maximum TOTAL_SALES within each county, or the standard deviation of all sales within each county.

The result is a map where the color of each area is based on the total number of points divided by the size of the area. Dividing counts by area is known as normalization, and it is a technique cartographers always use to display data by areas. Normalization helps to better understand spatial patterns because the size of the area is taken into account when areas are visually compared to each other.

If Use current map extent is checked, only the features in the analysis and area layer visible within the current map extent will be analyzed. If unchecked, all features in both the analysis layer and the area layer will be analyzed, even if they are outside the current map extent.

## Choose area

Select an area layer from the web map to which the points will be aggregated. If there are no boundary layers in the web map, you can select from the list of boundary layers available to you in ArcGIS Online. Any points that fall within the boundaries of areas within this layer will be counted and optionally summarized using your choices of statistics.

## Keep areas with no points

Determines whether areas that have no points within them appear in the result layer. If unchecked, areas without points will not appear in the result. If checked, areas without points will appear in the result.

## Add statistic

You can calculate statistics about attributes of the input point layer such as sum, mean, minimum, maximum, and standard deviation. The result layer will contain a new attribute for each statistic calculated. Any number of statistics can be added by choosing an attribute and statistic (a new drop-down box will appear).

## Choose field to group by

You can create statistical groups using an attribute in the analysis layer. For example, if you are aggregating crimes to neighborhood boundaries, you may have an attribute Crime_type with five different crime types. Each unique crime type forms a group, and the statistics you choose will be calculated for each unique value of Crime_type. When you choose a grouping attribute, two results are created: the result layer and a table containing the statistics for each unique group.

## Result layer name

This is the name of the layer that will be created in your My Contents and added to the map. The default name is based on the analysis type and the input layer name. If the layer already exists, you will be asked to confirm if you want to overwrite it.

Using the Save result in drop-down box, you can specify the name of a folder in My Contents where the result will be saved.