A time series is a collection of observations made sequentially through time. Each observation or value in the series has a time index. GoldSim contains a Time Series element which provides a way to input a time series into a GoldSim model.
Time Series elements provide a very flexible and powerful way to input external time histories of data into GoldSim (i.e., a table showing how a variable changes as a function of time). You can use a Time Series element to input the predefined histories of things like interest rates, commodity prices, temperature, cash flows, or the condition of a machine or a material.
Instantaneous Value Time Series
In this example, the input data represent the instantaneous price of a commodity at specified points in time.
The Primary Output is computed by linearly interpolating between the specified points at every update (i.e., timestep. For example, at Time = 250 days, the Value output would be $274.50 (halfway between 279 and 270). The Rate_of_Change output is computed by differentiating the specified values. Hence, between 200 and 300 days, the Rate is -$9/100 days = -0.09 $/day.
Discrete Change Time Series
This example illustrates the use of a Time Series where the input data represent discrete changes at specified times. The input data represent discrete changes to gasoline prices.
When the input data represent discrete changes to a variable at specified times, the Primary Output is a discrete change signal that are instantaneous quantities and cannot be directly plotted. An Integrator is used to represent the current gasoline price.
A detailed explanation of this model can be found by searching the GoldSim Help index for "Time Series element" and selecting "discrete changes."
Constant Values Over Specified Intervals
This example illustrates the use of a Time Series where the input data represent constant values over specified intervals. The input data represent the average temperature over specified time periods. The Primary Output is computed by assuming that the specified values stay constant over the time intervals between data points.
The Rate_of_Change output is also computed. Because the value is assumed to remain constant between data points, and then jumps discontinuously, the Rate is zero between data points, and then “spikes” when the Value changes. Theoretically, the derivative at this point is infinite. GoldSim computes the derivative as the difference between values divided by the timestep length. As such, the Rate_of_Change is somewhat arbitrary.
You can find a detailed description of this model by searching the GoldSim Help index for “Time Series elements” and selecting “constant values over intervals.”
Changes Over Specified Intervals
This example illustrates the use of a Time Series where the input data represent changes over specified intervals. This option is usually used to output cumulative values and/or rates that are specified by defining incremental changes in a variable over specified intervals.
In this example, the input data represent the total rainfall over specified time periods.
To Open the Model File:
- Start GoldSim
- Click on the File and select Open Example...
- Browse to General Examples --> TimeSeries
- Select the file called BasicTimeSeries.gsm