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  • Glossary

Values Graph

The values graph presents archaeologists' traditional visual display of the effect of the current ordering or seriation on the calculated values for each individual feature (for a plot of the input data, see Data Graph). The graph is particularly useful for judging the quality of a seriation when trying to maximize unimodality which will be reflected in lenticular or battleship shaped curves for each feature. The values graph plots selected items (selected in the Artifacts or Assemblages table) along the vertical axis against selected features (selected in the Features table) along the horizontal axis. For each item-feature pair the graph presents a horizontal bar or box depicting the corresponding value from the Values table. Users may choose which features to include in the graph using the Graph check box in the Features table. Right clicking anywhere on the graph will bring up a popup menu that gives a range of options for manipulating the graph. In the graph below zero values are depicted in a color other than black to distinguish them from very small non-zero values.

The values graph has traditionally been used in frequency seriation. However, it is equally valuable in other types of seriation - the values plotted need not be frequencies. For example, the plot below includes normalized data, some of which is negative as it is expressed in standard deviations. In this case the width of a box (or bar) is not the input data value, nor the corresponding computed normalized value, but the computed value minus the minimum value for the feature. The minimum value (a difference of zero) is represented by a magenta (or user set color) line to distinguish it from from very small non-zero differences. Red lines indicate negative values and black lines indicate positive values. Therefore, a feature value of +3 standard deviations, where the minimum value for the feature might be -2 standard deviations, would be represented by a box the red inner portion of which had a width of 2 and the black outer portion a width of 3 for a total width of 5 = 3 - (-2). Zero values can be plotted in a color other than black or red.

Frequencies Graph Popup Menu

There are ten items on the frequencies graph popup menu. These items are all also available on the Frequencies option of the Graphs item on the main menu of OptiPath.

Hide Graph will close the window containing the values graph.

Hide/Show Legend is a toggle to hide or show the graph legend which identifies the graph line colors for the different types of feature values graphed.

Set Axis Labels allows the user to set the axis labels. The default values are blank for both axes. The artifact/assemblage names are listed along the Y axis and the feature names are along the X axis. These cannot be changed by the user but an additional label for each axis can be added.

Save Graph saves the graph to a separate graphics file. The graph can be saved as a graphics file in a variety of formats (GIF, JPEG, PNG, BMP, TIFF, EMF).

Confidence Intervals will bring up a submenu that give a list of options for including confidence intervals on the graph. The first is Show/Hide Intervals which will display/hide confidence intervals on the graph and the second is Set Level which will allow you to specify the confidence interval to use. Confidence intervals are only available if you are using frequencies (Use Frequencies on the Seriations table), and if the numerical entries in your data are all integer. For more information see Confidence Intervals.

Bars/Boxes is a toggle to change the display between boxes and bars. Even if the display is using boxes, unknown values will be represented by bars. If confidence intervals are being displayed, data values are automatically displayed as boxes and the Bars/Boxes toggle allows you to change the confidence interval between boxes and bars. The advantage of using boxes is that vertical lines are centered on the value being displayed while bars can be deceiving. This is because the length of a bar will change as its thickness is changed (the termination or "cap" of each bar being a circle which grows with the width). 

 

Lines will bring up a submenu with three choices: Boxes, Bars and Intervals. Each of these choices wil bring up a subsubmenu with two choices: Increase and Decrease. Clicking on these will increase or decrease the corresponding lines on the graph.

Show/Hide Earlier/Later is a toggle to include/exclude the virtual Earlier and Later items in the display.

Set Colors will bring up a submenu that allows users to choose colors for each of the data types, or reset all types to the default colors.

Help will bring up this documentation.