There are several input modes available. For each of them there are control parameters that can be set.
Constant (with slider)
sets the variable to behave likes a constant which you will be able to control with a slider. You can set the minimum and maximum range for the slider. Once you have done this a slider will appear and you can change the range on the slider just as you would any other. This option is not available for constants, since these are sliders normally.
Step Change sets the variable to start at the From value and then change to the to value when Time reaches the value specified for at time.
Ramp sets ramp behavior starting at the from value, holding constant till the starting at time value then ramping up or down to the to value at the time specified by finishing at after which it will again be constant.
Exponential Growth sets exponential growth from the initial value Starting from, remaining constant until changing after time and then growing exponentially at growth rate (%/unit time) for the rest of the simulation. Note that the number 2 means 2%/year (or .02/year) if the model has time in years (independent of the value of TIME STEP).
Exponential Decay sets an exponential decay (decreasing at an ever decreasing rate toward 0). The variable will start at Starting from and remain constant till changing after time then it will decay at decay rate for the rest of the simulation. Note that the decay is in percent per unit time so that if the model is in months 5 means 5%/month (independent of the value of TIME STEP).
Sine Wave creates a sine wave that goes from the value Between to the value and (note that the second value can be larger or smaller than the first) and has the period specified by with period. The wave will start in the middle of the two values, and maintain that value till mean value till time then go up to the second value, turn and go down to the first and so on.
Pulse creates a pulse of input that stays at Base Value until the time specified in at time when it takes on the values specified in pulsing to and holds that value for the time specified in for duration. After that it returns to Base value. If duration is 0 the pulse will last a single TIME STEP.
Pulse Train creates a train of pulses starting at Base value and then going up to pulsing to at the time specified in repeating every for the time specified in for duration. The value then returns to Base value till time is twice repeating every then the pulse repeats.
Square Wave creates a square wave that goes from the value Between to the value and (note that the second value can be larger or smaller than the first) and has the period specified by with period. If the mean value till time is after the model’s initial time the variable will take on the mean of the two values. After mean value till time the wave will move to the first value, then go to the second value after ½ of the period has passed. After another ½ the period passes it will return to the first value and continue in this manner for the rest of the simulation.
Freeze at Time captures the variable's value at the time specified by at time and holds it at that value for the remainder of the simulation. Before at time the variable follows its normal model equation.
Freeze Between Times holds the variable at its model value from the time specified by from time through the time specified by to time. Outside this window the variable follows its normal model equation.
Freeze Until Time holds the variable at its initial value until the time specified by until time and then releases it to follow its normal model equation for the remainder of the simulation.
Limit leaves the variable following its normal model equation but keeps the computed value between min and max. On a Level the bound also holds the rate: while the Level sits at a bound, a net rate that would push it further outside is zeroed, while a rate bringing it back inside acts normally.
Perturb variable multiplies the variable's computed value by (1 + r), where r is the Perturbation (r) parameter. For a Level the perturbation is applied to its net rate of change, leaving its initial value unchanged; when the value is at or near zero, r is added rather than multiplied. Perturbing a Level nudges a system state, while perturbing an Auxiliary changes the gain of a single link — to test a particular feedback loop, perturb a variable on that loop. A tiny r (such as 1e-8) confirms gains predicted by linearization; a larger one (such as 0.1) tests the response at realistic magnitudes.
Perturb variable between times applies the same perturbation only during the time window from Start Time (inclusive) up to End Time (exclusive).
NOTE Limit and the two Perturb modes act on values the model itself computes, so they are not offered for variables that take their values from data.
