Using other helpers

Because of the ease with which new helpers can be developed (see below for details) a great many other helpers exist, alongside the plotter and the data table. These helpers are of a variety of ages and provenances, and do not conform to any consistent interface. Some were developed for specific applications, and although they are of general interest, reflect their origins in their design.

In order to use a helper, your model firstly needs to be built: that is, you need to have selected the "Build" item from the "Model" menu, as described in Running Models. Almost all these helpers work best in the multiple-windows run time environment. The procedure for adding helpers differs, depending on whether the single or multiple-window run time environment is selected.

• in the single-window run time environment, add helpers using the "Add" menu; or
• in the multiple-windows run time environment, add helpers using the "Add tool" submenu in the "IOTools" menu.

The other helpers included in the standard installation of Simile are:

• Plot value against time
• Lollipop diagram
• Spatial grid display
• Polygon diagram (map)
• Sounds for events
• 3d viewer
• Time profiles

With the exception of the "Plot value against time" helper, all these helpers are primarily designed to display data from multiple-instance submodels. The spatial grid display and the three-dimensional viewer are designed to display data from multiple patches of land. The time lollipop display and the time profiles helper are designed to display the attributes of each instance of a population submodel. All these helpers use the following procedure for binding variables.

There are a few other tools, which don't actually perform the input/output functions of helpers but which are implemented as helpers because they operate on the executing model. One  is used to initialise the pseudo-random number generator:

 Initialise pseudo-random number generator

Another is used to alter the behaviour of functions defined by sketch graphs:

 Edit function sketch graph

New to Simile v6: a tool which saves selected model values to file each time step:

 Data logger 

Binding variables to helpers

When you select, for example, the "Plot value against time" helper, you need to specify which variable in your model will be plotted. Therefore, the helper issues an instruction, asking you to select a variable by clicking on it in the model explorer or in the model diagram window. Other helpers require more than one variable: in these cases, the instructions indicate the sequence in which the variables should be selected. For example, the "Lollipop diagram" helper (which displays trees in three dimensions) requires you to click first on a variable representing the x-coordinate of each tree; then on one representing the y-coordinates; then on one representing the heights. Note that no checks are made to ensure that the variable you select for x-coordinates really does contain x-coordinates: it is up to you to choose the right one.

Each helper uses one of two methods for instructing you to select the necessary variable(s):

• Separate instruction window: a small window instructing you to click on a model element. The window will tell you the role of the variable that you are selecting in relation to the helper's task, and you need to click on a variable that is appropriate to that role.

• Instructions in the helper window: an instruction about what you should be doing in the helper window itself. One example is the slider input helper. Typically, this allows you to repeatedly select variables from the model, with each one being added to the helper.

Developing new helpers

Simile is probably unique in the world of visual modelling software in that no input/output tools are built into the software. Rather, every such tool is implemented as a separate program in an industry-standard interpreted language called Tcl/Tk. When you load Simile, it creates a list of available helpers by looking in the "IOTools" directory for appropriate files. This is the list of helpers that is then bound into the menus.

One advantage of this approach is that with simple programming anyone can implement a helper customised to their own requirements: there is no need to submit a request to Simulistics (though you are, of course, welcome to do so). This means that if you are modelling (for example) whales, you can implement a display helper that shows whales swimming around. These helpers can be distributed easily, as simply copying the file to the "IOTools" directory is sufficient to install the helper in each copy of Simile.

In: Contents >> Running models >> Working with helpers