Specifying Time Series Outputs

After you have defined the time series data (the input), it is necessary to define what outputs are to be produced by the element. That is, you must specify how GoldSim should manipulate the time series input data to produce one or more time series outputs that can subsequently be used in your model.

By default, GoldSim produces a single output, which (if the output is a value, as opposed to a discrete change) corresponds to the instantaneous value of the output at each point in time (i.e., at each model timestep), computed by simply interpolating between the specified data points. In many cases, this will meet your needs, and there is no reason to modify this.

However, in some cases, you may want to take advantage of some advanced features of the Time Series element when specifying Time Series outputs. To access these features, you must press the More button on the Time Series dialog:

The first two options in this section pertain to options for specifying Time Series outputs.

Because the time series data can be specified at arbitrary time points (that are unrelated to the timesteps used in the GoldSim model), GoldSim allows you to specify exactly how the time series will be mapped to timesteps in GoldSim. GoldSim provides two options for the Primary Output:

If Instantaneous value is selected (the default), GoldSim computes the instantaneous value of the output at each point in time (i.e., at each timestep).

If Average value over the next timestep is selected, GoldSim averages the output over the projected timestep length. This option should be selected when your time series represents flows or fluxes, as by doing so, you ensure that the flow or flux is properly conserved.

Note: If your input data represents Discrete Changes (i.e., the data Type has been defined as a Discrete Change Signal, rather than a Value), the only option available for the Primary Output is "Discrete Change". In this case, the element will generate Discrete Change Signals with an Add instruction at the specified time points (and independent of the scheduled timesteps).

In addition to the primary output, you can also choose to produce a secondary output that represents the Rate of Change of the variable. This is done by checking the Enable Rate of Change output option:

If this box is checked, the element computes a secondary output (called Rate_of_Change). It represents the rate of change of the variable over the next projected timestep. The display units for this output are the display units for the Time Series divided by the Time Display Unit defined in the Simulation Settings dialog.

The Rate_of_Change output is valuable when the data you have collected represents changes in the cumulative value of a variable (e.g., cumulative sales, cumulative rainfall) over specified intervals, and you are interested in computing average rates between the measurement points (e.g., sales rates, rainfall rates). In these cases, you enter changes in the cumulative value of a variable between the measurement points (e.g., every week or every month, or at irregular intervals), and specify that the data represents a "Change over the next time interval". You then specify that you want to "Enable the Rate of Change output". The Rate_of_Change output then represents the average rate (e.g., rainfall or sales rate) for each interval (e.g., month).

Note: Because GoldSim computes the Average Value over the next timestep primary output and the Rate_of_Change secondary output by assuming a timestep length, and under some circumstances the timestep length could subsequently be shortened (due to an event), the values that are computed could contain a slight error. In such a case, GoldSim tracks any error that is incurred, and corrects for it at the next timestep (in order to ensure conservation of the variable).

Note: If the input represents an Instantaneous value, and the last data point corresponds exactly with the end of the simulation, the Rate_of_Change output drops to zero at the last timestep (since GoldSim cannot compute a "forward looking" rate of change at that point).

Note: The Rate_of_Change output is not available if your input data represent Discrete Changes.