Description
Return exp(-decayRate × travelTime) and opportunities times weight times that decay.
Spatial models compare distances, travel intervals, activity areas, or supplied interaction functions. Coordinates and model parameters must share a compatible basis, and a local term does not establish observed behavior.
Return exp(-decayRate × travelTime) and opportunities times weight times that decay.
When to use this tool
Use Accessibility One Destination Decay Term when you need one explicit spatial or travel-model component.
How to use the tool and how it works
- Enter opportunities, travelTime, decayRate, weight. Use the units and conventions below.
- Run the tool. Correct any format, range, or cross-field input error before interpreting the output.
- Read decay, contribution. Use the output convention below.
Require nonnegative opportunities, travelTime, decayRate, and weight. Return exp(-decayRate × travelTime) and opportunities times weight times that decay.1
| Input field | Meaning and units | Accepted input |
|---|---|---|
| opportunities | Opportunities | Required. Finite number; minimum 0. |
| travelTime | Travel Time | Required. Finite number; minimum 0. |
| decayRate | Decay Rate | Required. Finite number; minimum 0. |
| weight | Weight | Required. Finite number; minimum 0. |
| Output field | Interpretation | Returned shape |
|---|---|---|
| decay | Decay | Required. Finite number. |
| contribution | Contribution | Required. Finite number. |
{
"input": {
"opportunities": 100,
"travelTime": 10,
"decayRate": 0.06931471805599453,
"weight": 0.5
},
"output": {
"decay": 0.5,
"contribution": 25
}
}Limitations and assumptions
- DecayRate is inverse time; this is one destination contribution without summing destinations, competition, capacity, or evidence of realized access.
- Inputs must satisfy both the field types and the cross-field conditions above. Invalid input causes an error; a successful false flag or documented placeholder is a different result.
- Numeric calculations use binary floating point unless exact decimal-integer arithmetic is explicitly stated. No hidden measurement tolerance or decimal rounding is added; nonfinite or out-of-contract results are rejected. Numeric signed-zero results are exported as zero.
Alternative or Complementary methods
Check projection, route definitions, calibration, and the complete model before interpreting access or predicted flows.
References
Similar or alternative tools
- Spatial Interaction Distance Deterrence Term
Return exp(-distance/scale) when exponential, otherwise (1+distance/scale)^(-power).
- Gravity Flow One Origin Destination Term
Multiply nonnegative coefficient, originMass, and destinationMass and divide by positive distance raised to supplied exponent.