Now that we have looked at the mappers individually, it is time to combine them to the final product -- the plot.
This is done by the creation of a mapper stack, which is an ordered list of configured mappers that are called one by one to generate the contents of the plot on the network plane. The mapper control dialogs of these mappers (except for those whose control windows are disabled by the corresponding mapper flag) are arranged in the form of a tabbed dialog, where the tabs are arranged from right to left, having the first drawn mapper (background) on the right, the last (foreground) on the left. This is illustrated in Figure 20, which combines some of the mappers taken from the examples of the previous section, in the following order:
The parameter grouping mechanism, which was presented earlier, is an important feature when combining mappers. As each mapper has its own set of parameters, when combining several mappers to a plot, often some of these parameters correspond to the same logical value. E.g. the offset of a link value bar normally corresponds to the offset used for the link base, or, when displaying several volumes in a multi-layer band width plot, the same scale is usually used for all of them. Without an automatic synchronization of these values between the different mappers, the user would be obliged to change all these value separately for each mapper -- which might become quite cumbersome, even for simple plots.
The parameter grouping allows associating an optional group name with each parameter. Subsequently, when a parameter value in one mapper is changed, the change is signaled to all other mappers, which in turn propagate the signal to their own parameter list, causing parameters with the same group name (and compatible value type) to be updated.
An example using parameter grouping is illustrated in Figure 21. This plot is defined as the combination of five mappers (from back to front): simple white background mapper with its control dialog disabled, transit segment value mapper for the volumes of the express bus lines, transit segment value mapper for the volumes of the standard bus lines, link base mapper and node box mapper. The following parameter groupings are used in this plot configuration:
A mapper control manager implements all the functionality needed to create and edit the mapper stack. It provides the following operations:
A plot configuration (or often just short ``plot'') is defined by a stack of fully configured mappers and some additional parameters related directly to the plot, such as plot flags, name, description, caption and icon text and the name of the active mapper.
Note that a plot configuration is not directly dependent on a particular EMME/2 application or scenario, but can be used with any network. When a new network is loaded, e.g. after switching to a different scenario, the mappers automatically resynchronize their network dependent parameters. Of course, if mappers access user defined network attributes, these have to be defined in the new network, otherwise the expressions will be signaled as invalid.
The current plot configuration can be saved to a file and reloaded again later on, whenever the user wishes to produce the same type of plot again. In addition, plot configuration files can be registered in the users preferences, so that they will be accessible directly on the Enif ``Plot'' menu by their name.
In the remaining part of this section, the possibilities of Enif are illustrated by some example plots which were produced using the standard Winnipeg EMME/2 demonstration data bank.
|Fig.22||A simple plot composed only of a background mapper, a node polygon mapper and some legend texts. It uses an indexed stylus with linearly interpolated fill colors to produce a zone map showing the different levels of car ownership in different colors.|
|Fig.23||This plot is composed of a satellite picture in the background on which are overlaid an annotation of the rivers (they don't really fit the satellite image to well...) and a ``street'' network layer composed of several link base mappers.|
|Fig.24||A detailed auto volume plot which shows link and turn volumes.|
|Fig.25||A typical bandwidth plot showing the auto, transit and auxiliary transit assignment results as a multi-layer volume plot.|
|Fig.26||This plot shows the distribution of vehicle miles traveled by auto speed. An indexed stylus using a linear color interpolation is used to color the bars by speed from red (very slow) to dark green (very fast). In order to visualize where the different speeds occur on the network, a small network plot is superimposed on the top right corner by means of a link base mapper using the same indexed stylus.|