Assemblages
Assemblages are collections of artifacts. Archaeologists often deal with assemblages rather than individual artifacts. For example, an investigator might be concerned with dating all of the artifacts found together in a particular stratigraphy layer rather than trying to date the individual items themselves. OptiPath can work with collections as individual artifacts, or it can build assemblages from individual artifact data.
By choosing Assemblages in the seriation parameters
or by selecting Assemblages | Use Assemblages from the OptiPath main menu
or by clicking the Assemblages button
on the
toolbar,
you can direct OptiPath to classify individual artifacts by their assemblage
and then seriate the assemblages rather than the artifacts themselves. The
implication is that frequency seriation will be
used to seriate the aggregated assemblage data; however, this is not required.
The Assemblages button is a toggle, being replaced by the Artifacts button
when you are currently using
assemblages.
When using assemblages, OptiPath automatically aggregates artifact data into assemblage data. It does this by accumulating (adding) the values for a particular feature for all artifacts in an assemblage and then using that accumulated value as the feature value for the assemblage. In the screen shot below, the assemblage Layer 2 does not include the values for the artifact Scraper because that artifact has been excluded.
Normally artifact data represent occurrences of a feature. If the artifacts represent individual items, then the artifact data would most likely be zero or one. Generally, an artifact must either possess the feature, or not; but this is not required - artifact feature data may be fractional.
If the artifacts in your data are themselves really collections of artifacts, then more than one artifact in the collection may possess a particular feature and the data value for that artifact-feature combination may be an integer greater than one. For example, each artifact might represent a collection of items found within a particular stratigraphy layer inside a single structure in a site that contains a number of structures. The assemblages might be stratigraphy layers. Then the data value for an "artifact" might be a positive integer representing the number of items from a single stratigraphy layer in a particular structure that possess a given feature. In this example, features for ceramics might be "glazed" and "unglazed" and the artifact data might represent the number of sherds of each feature type found in a particular stratigraphy layer in a single structure.
Alternatively, you may enter the fraction or percentage of artifacts in the collection that possess the feature. If assemblages are stratigraphy layers, then the assemblage data might represent the frequencies with which glazed and unglazed sherds occurred over all structures for each stratigraphy layer.
The Assemblages menu contains a number of items:
Edit - allows you to open the assemblages table and create, delete and edit the assemblages and edit their parameters.
Include All - allows you to include all excluded assemblages in the next seriation.
(Don't) Use Assemblages - a toggle that allows you to (not) use assemblages in your next seriation. Not using assemblages is equivalent to using artifacts. This item toggles between Use Assemblages and Don't Use Assemblages. There are corresponding Use Assemblages
Show (Hide) Data - a toggle that specifies whether artifact feature data is to be displayed in the assemblages table. This item toggles between Show Data and Hide Data. This item toggles between Show Results and Hide Results. This menu item is disabled if the assemblages table is not open.
Show (Hide) Results - a toggle that specifies whether seriation results are to be displayed in the assemblages table. This item toggles between Show Results and Hide Results. This item toggles between Show Results and Hide Results. This menu item is disabled if the assemblages table is not open.
In the Assemblages table you may add, edit and delete assemblages and edit their data. There are a number of attributes associated with each assemblage:
Exclude - this parameter allows you to exclude an assemblage temporarily from your seriation. The alternative is to delete the assemblage in which case all information and data related to the assemblage will be lost to this seriation permanently. In contrast, using Exclude allows you to resurrect the assemblage and its data by clearing the Exclude field.
Index - an integer value assigned to an assemblage that allows you to sort assemblages in a list.
Assemblage - a name that uniquely identifies the assemblage. Assemblage names are restricted to 50 characters. The assemblage name is required for each assemblage. An assemblage cannot have the same name as another assemblage and cannot have the same name as an artifact. The following names are reserved for use by OptiPath and cannot be used as assemblage names: Earlier, Later, OPS Index, OPS R Squared.
Description - an optional description that can be entered for each assemblage. There is no limit to the length of a description.
Earliest - an integer value representing the earliest possible date that can be assigned to this artifact. The Earliest date should not be less than the overall Earliest date for the seriation which is set in the Seriations table. If you use an earliest date other than earliest date for the overall seriation, OptiPath will use a different objective function and a different algorithm to solve the seriation and computation times will be noticeably longer - see Optimal Path Seriation.
Latest - an integer value representing the latest possible date that can be assigned to this artifact. The Latest date should not be greater than the overall Latest date for the seriation which is set in the Seriations table. If you use a latest date other than latest date for the overall seriation, OptiPath will use a different objective function and a different algorithm to solve the seriation and computation times will be noticeably longer - see Optimal Path Seriation.
If you elect to show results by choosing Assemblages | Show Results from the Assemblages menu,
then you will see two additional columns, Order and Date, giving information about the current seriation:
Order - this parameter indicates an assemblage's sequential (ordinal) position in a seriation. This field cannot be modified by the user. However, you can reverse the order of the seriation by choosing Seriate | Reverse from the OptiPath main menu or by clicking the Reverse button
on the toolbar.
Date - this parameter indicates an assemblage's date as estimated by OptiPath in performing a seriation. Dates are are always given as an integer intending to represent a year. Although OptiPath calculates precise dates it rounds them to the nearest year. Users who need greater precision can refer to the Distance field in the Results window which is used by OptiPath to calculate the date. This field cannot be modified by the user.
This information can also be seen in the Results table.
If you elect to show data by choosing Assemblages | Show Data from the Assemblages menu, then you will also see columns for the data for each of your features.
Features - there is a separate column for each feature. Feature names cannot be edited in this table. Each cell in a feature column reflects the value of the measure for that feature for assemblage in the corresponding row. Values can be numbers or letters or words, depending upon the feature data type.
You can enter and edit your data in this table or you can edit them in the Data table or in the Results table.
