Specifying the Inputs to an Integrator

The Display Units The units (e.g., m, g, $/day) in which an output is displayed within GoldSim. determine the dimensions An output attribute for an element that defines the dimensionality (in terms of Length, Time and other fundamental dimensions) of the output. of the Integrator's output. This output can only be specified as a value (it cannot be a condition), and can be specified as a scalar An output consisting of a single value or condition., a vector A one-dimensional array. or a matrix A two-dimensional array.. You can specify whether the Integrator is a scalar, vector or matrix by pressing the Type... button. By default, the output of a new Integrator element An stock element that integrates rates. is a scalar, dimensionless value.

The Initial Value input to the Integrator must have the same attributes (order and dimensions) as the output.

Note: The Initial Value must be a number or a link from a static variable (e.g., a constant Data element An input element intended to represent constant inputs in a model. or some other output that does not change with time).

The Rate of Change input (which can be positive or negative) must have the same order, but the dimensions must represent a rate of change of the output (e.g., if the output has units of length, the Rate of Change must have units of length per time).

Note: The specified Rate of Change represents the constant rate over the next timestep A discrete interval of time used in dynamic simulations.. Hence, if a Rate of Change was defined as “if(time > 10 day, 2 m/day, 1 m/day)”, and you were using a 1 day timestep, the rate would not actually change to 2 m/day until time = 11 days. That is, since at time = 10 days, the if statement indicates that the rate is equal to 1 m/day, GoldSim would assume that the rate was equal to 1 m/day between 10 days and 11 days. If you wanted the rate to change at 10 days, you would write the if statement as “if(time >= 10 day, 2 m/day, 1 m/day)”.

Note: If the output of an Integrator is specified as being an array A collection of variables that share common output attributes and can be manipulated in GoldSim elements or input expressions. (a vector or a matrix), the inputs (Initial Value and Rate of Change) must, by definition, themselves be arrays. Since you often may wish to enter a zero array (a vector or matrix of zeros) for the Initial Value or the Rate of Change, GoldSim allows you to leave one or both of these input fields blank, in which case it interprets the field as a zero array.