Analysis (Process operations)

Buffer

Creates a buffer around an Item.

Radius*: The buffer radius as a simple value or as an expression.

See also Buffer command.

Buffer (inside)

Creates a buffer around the boundary of a Polygon that only contains the parts that are inside the Polygon.

Radius*: The buffer radius, as a simple value, or as an expression.

See Buffer command.

Buffer (interior)

Creates a buffer inside a Polygon that excludes the parts of a doughnut buffer around the boundary of the Polygon.

Radius*: The buffer radius, as a simple value, or as an expression.

Buffer (outside)

Creates a buffer around the boundary of a Polygon that only contains the parts that are outside the Polygon.

Radius*: The buffer radius, as a simple value, or as an expression.

Buffer (variable)

Creates a buffer around the boundary of a Polygon that only contains the parts that are outside the Polygon.

Start and End Radius*: The buffer start and end radii, as a simple value or as an expression.

Example: '12.34* or Max(123.4.Sqrt(_area#))'

Cluster

Clusters Items together within regular, rectangular grid cells.

Property	Value
Cell height*	The height of a cluster grid cell, as a simple value, or as an expression, e.g. '12.34', or '_sx#/12'
Cell width*	The width of a cluster grid cell, as a simple value, or as an expression, e.g. '43.21', or '_sx#/34'
Origin X	The X coordinate of the origin of the cluster grid, as a simple value, or as an expression, e.g. '12.34', or '_ox#'
Origin Y	The Y coordinate of the origin of the cluster grid, as a simple value, or as an expression, e.g. '43.21', or '_oy#'

This function aggregates items within a grid of a user-defined size. Items found within a grid cell are represented in the output by a point item with an attribute that shows the sum of the items it represents.

Examples of use may include aggregating data for use at lower scales where exact geographic location is less important than knowing how many items there are.

This example shows the result of the Cluster function:

Create Thiessen Polygons

Creates Thiessen Polygons of influence around the hook point of Items.

Property	Value
High X	The high X (right) value of the extents box of the Thiessen Polygons as a simple value or as an expression.
High Y	The high Y (top) value of the extents box of the Thiessen Polygons as a simple value or as an expression.
Low X	The low X (left) value of the extents box of the Thiessen Polygons as a simple value or as an expression.
Low Y	The low Y (bottom) value of the extents box of the Thiessen Polygons, as a simple value, or as an expression.
Margin	The margin by which the extents should be padded, as a simple value, or as an expression.

See Spatial Analysis-Thiessen Polygons and the Thiessen Polygons command for an example of creating a Thiessen Polygon.

Dissolve

Merges Items based on attribute values.

Expression*: The merge value, as a simple property name, or as an expression.

Example: _area#>1000

The initial map with areas shown by a Labels theme:

All the selected items that match the Expression*_area#>1000, are merged together (Boolean Union) into a single item:

The rest of the selected items are merged into another single item:

See also Dissolve command.

Geodetic buffer

Creates a 'geodetic' buffer around an Item i.e. a buffer that takes the curvature of the Earth into account.

Property	Value
Distance*	The geodetic buffer radius in metres as a simple value or as an expression, eg '12.34' or Max(123.4,Sqrt(_area#))'.
Number of points	The number of points to use when calculating the buffer as a simple value or as an expression, eg '64' or 'Max(64,Int(Floor(0.5*(_sx#+sy#))))' ( the default value is 4.

Getis-Ord Gi*

Calculates the Getis-Ord Gi* statistic for each feature in a dataset.

Property	Value
Distance	This is the threshold distance when performing a search for polygons in the local neighbourhood; any polygons with centroids outside this distance will be ignored when calculating the local average value. This option is only used when the Relationship (see below) parameter is set to Inverse distance, Inverse distance squared, Fixed distance band or Zone of indifference. If no other centroids can be found within this distance, the Z and P values for the polygon will not be set and a further column will be created in the schema holding an error value.
Distance method*	Select the required distance measure: Euclidian: As the crow flies, ie a straight line. Manhattan: Imitates moving across a city block: distances are traversed at right angles i.e. the sum of the difference between the two point coordinates.
Expression	Analysis variable to calculate Gi* statistics on eg CrimesTotal# The input value for analysis, as a simple property name, or as an expression, eg 'IncidentCount&' or 'NumIncidentsJan& + NumIncidentsFeb&' The expression must be appended with the # / & /$ symbol.
Number of neighbours	The number of neighbours to factor in to the local average calculations when using the K Nearest Neighbours Spatial Relationship parameter – will search for that many of the nearest centroids to the centroid of the polygon being calculated upon.
Relationship*	Conceptulization of spatial relationship. Inverse distance The weighting for features will decrease regularly with distance from the original centroid up to the distance threshold Inverse distance squared Same as Inverse Distance, however the weighting will decrease more severely with distance. Fixed distance band Every polygon within the distance threshold is counted as being ‘in’ and weighted 1, everything outside is counted as ‘out’ and weighted 0. Zone of indifference Combination of Fixed Distance band and Inverse Distance. Everything inside the threshold is ‘in’ and weighted 1, after this point the weighting tapers off towards 0. K Nearest Neighbour Will search for the K nearest centroids to the polygons centroid and use these as the Local Neighbourhood with weightings of 1, any others will be ignored (weighted 0).

Intersect

Combines the Items using the intersect boolean operation, i.e. only overlaps are kept. No input values required.

Property	Value
Filter Expression	A filter expression, e.g. '_FC& IN (1,2,3)' or 'grid_type$="DEM", to use when finding the source Grid Items.
Overlay*	The name of the Overlay containing the source Grid Items.
Radius*	The 'Viewshed' radius, as a simple value, or as an expression, e.g. '12.34' or 'Max(123.4,broadcast_range#)'

Property	Value
Filter Expression	A filter expression, e.g. '_FC& IN (1,2,3)' or 'grid_type$="DEM", to use when finding the source Grid Items.
Overlay*	The name of the Overlay containing the source Grid Items.
Radius*	The 'Viewshed' radius, as a simple value, or as an expression, e.g. '12.34' or 'Max(123.4,broadcast_range#)'

Property	Value
Filter Expression	A filter expression, e.g. '_FC& IN (1,2,3)' or 'grid_type$="DEM", to use when finding the source Grid Items.
Overlay*	The name of the Overlay containing the source Grid Items.
Radius*	The 'Viewshed' radius, as a simple value, or as an expression, e.g. '12.34' or 'Max(123.4,broadcast_range#)'

Property	Value
Cellsize*	The QZone cell size, as a simple value, or as an expression.
Radius	The buffer radius, as a simple value, or as an expression.