Computes and assigns the cost of the shortest path from a source object to each connected object as the Z-values or measure values of the input features.
Input Line features must be a topologically noded network with features connecting at line ends only. That is, all features must be split at junctions.
There can only be one Source input for each group.
All lines that are connected to the Source input port are output through the Connected port.
The lines that are not connected to the Source input port will be output through the Disconnected port. If Output Optimal Cost As parameter is set to Z-Values, the dimension of the disconnected lines is set to 2D. Otherwise, disconnected lines are untouched.
There can only be one Source input for each group. All other inputs and non-linear features are output through the <Rejected> port.
Choose the attributes to group by.
Process At End (Blocking): This is the default behavior. Processing will only occur in this transformer once all input is present.
Process When Group Changes (Advanced): This transformer will process input groups in order. Changes of the value of the Group By parameter on the input stream will trigger processing on the currently accumulating group. This may improve overall speed (particularly with multiple, equally-sized groups), but could cause undesired behavior if input groups are not truly ordered.
There are two typical reasons for using Process When Group Changes (Advanced) . The first is incoming data that is intended to be processed in groups (and is already so ordered). In this case, the structure dictates Group By usage - not performance considerations.
The second possible reason is potential performance gains.
Performance gains are most likely when the data is already sorted (or read using a SQL ORDER BY statement) since less work is required of FME. If the data needs ordering, it can be sorted in the workspace (though the added processing overhead may negate any gains).
Sorting becomes more difficult according to the number of data streams. Multiple streams of data could be almost impossible to sort into the correct order, since all features matching a Group By value need to arrive before any features (of any feature type or dataset) belonging to the next group. In this case, using Group By with Process At End (Blocking) may be the equivalent and simpler approach.
Note: Multiple feature types and features from multiple datasets will not generally naturally occur in the correct order.
As with many scenarios, testing different approaches in your workspace with your data is the only definitive way to identify performance gains.
If Weight Type is set to By Length (Forward Only) or By One Attribute, then the weight of each input line is set to the length of the line or the attribute value specified in the Forward Weight Attribute. In this case, the algorithm will only consider the original orientation of the lines when computing the cost of the shortest path.
If Weight Type is set to By Length or By Two Attributes, then the shortest path algorithm will consider both directions of the input lines. If Weight Type is set to By Two Attributes, the original orientation of the input line has the weight specified in the Forward Weight Attribute and the reversed orientation of the input line has the weight specified in the Reverse Weight Attribute. If Weight Type is set to By Length, the weight of both the original orientation and the reversed orientation of the input line is set to the length of the line.
Only linear features with non-negative weight attribute values are allowed if the Weight Type is set to By One Attribute or By Two Attributes. If a feature does not have the attribute specified in the Forward Weight Attribute or the Reverse Weight Attribute, a zero weight is used for the line.
If this parameter is set to Z-Values, then the optimal cost for each connected node is set as the Z-value of the node. Otherwise, the optimal cost is set as the measure value of the node with the measure name specified in Measure Name.
If you leave the Measure Name empty, the default measure name will be used.
If this parameter is set to Yes, the transformer snaps the source points to the closest end points of the network lines.
The source points are only snapped to the network lines if they are within the tolerance specified in Snapping Tolerance.
Editing Transformer Parameters
Using a set of menu options, transformer parameters can be assigned by referencing other elements in the workspace. More advanced functions, such as an advanced editor and an arithmetic editor, are also available in some transformers. To access a menu of these options, click beside the applicable parameter. For more information, see Transformer Parameter Menu Options.
There are several ways to define a value for use in a Transformer. The simplest is to simply type in a value or string, which can include functions of various types such as attribute references, math and string functions, and workspace parameters. There are a number of tools and shortcuts that can assist in constructing values, generally available from the drop-down context menu adjacent to the value field.
Using the Text Editor
The Text Editor provides a convenient way to construct text strings (including regular expressions) from various data sources, such as attributes, parameters, and constants, where the result is used directly inside a parameter.
Using the Arithmetic Editor
The Arithmetic Editor provides a convenient way to construct math expressions from various data sources, such as attributes, parameters, and feature functions, where the result is used directly inside a parameter.
Set values depending on one or more test conditions that either pass or fail.
Expressions and strings can include a number of functions, characters, parameters, and more.
When setting values - whether entered directly in a parameter or constructed using one of the editors - strings and expressions containing String, Math, Date/Time or FME Feature Functions will have those functions evaluated. Therefore, the names of these functions (in the form @<function_name>) should not be used as literal string values.
|These functions manipulate and format strings.|
|A set of control characters is available in the Text Editor.|
|Math functions are available in both editors.|
|Date/Time Functions||Date and time functions are available in the Text Editor.|
|These operators are available in the Arithmetic Editor.|
|These return primarily feature-specific values.|
|FME and workspace-specific parameters may be used.|
|Creating and Modifying User Parameters||Create your own editable parameters.|
Dialog Options - Tables
Transformers with table-style parameters have additional tools for populating and manipulating values.
Enabled once you have clicked on a row item. Choices include:
Cut, Copy, and Paste
Enabled once you have clicked on a row item. Choices include:
Cut, copy, and paste may be used within a transformer, or between transformers.
|Start typing a string, and the matrix will only display rows matching those characters. Searches all columns. This only affects the display of attributes within the transformer - it does not alter which attributes are output.|
|Import populates the table with a set of new attributes read from a dataset. Specific application varies between transformers.|
Generally resets the table to its initial state, and may provide additional options to remove invalid entries. Behavior varies between transformers.
Note: Not all tools are available in all transformers.
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