Difference between revisions of "Dynamic and uncertainty"

(Created page with "Category:Analytica User Guide <breadcrumbs>Analytica User Guide > Dynamic Simulation > {{PAGENAME}}</breadcrumbs> __TOC__ ==See Also== <footer>Dynamic dependencies / {{...")
 
Line 4: Line 4:
 
__TOC__
 
__TOC__
  
 +
Uncertain variables propagate uncertainty samples during dynamic simulation. If an uncertain
 +
variable is used in a dynamic simulation, its uncertainty sample is calculated only once, in the initial time period.
 +
 +
'''Example:''' The following definitions model population changes over time:
 +
 +
Variable Population := Normal(30, 2)
 +
Variable Birthrate := Normal(1.2, .3)
 +
Time := 1 .. 10
 +
Variable Pop_by_year := Dynamic(Population, Self[Time - 1] + Birthrate)
 +
 +
[[File:Chapter17_14.png]]
 +
 +
 +
The uncertainty samples for Population and Birthrate are each calculated once, at the initial
 +
time period. The same samples are then used for each subsequent time period.
 +
 +
==Resampling==
 +
If you want to create a new uncertainty sample for each time period (that is, resample for each time period), place the distribution in the last parameter of the Dynamic() function. For example, replace Birthrate with its definition in Pop_by_year:
 +
 +
Pop_by_year := Dynamic(Population, Self[Time - 1] + Normal(1.2, .3))
 +
 +
An alternative way to create a new uncertainty sample for each time period is to make Birthrate a dynamic variable:
 +
 +
Birthrate := Dynamic(Normal(1.2, .3), Normal(1.2, .3))
 +
Pop_by_year := Dynamic(Population, Self[Time - 1] + Birthrate)
  
 
==See Also==
 
==See Also==
 
<footer>Dynamic dependencies / {{PAGENAME}} / Dynamic on non-Time Indexes</footer>
 
<footer>Dynamic dependencies / {{PAGENAME}} / Dynamic on non-Time Indexes</footer>

Revision as of 23:20, 17 December 2015

Uncertain variables propagate uncertainty samples during dynamic simulation. If an uncertain variable is used in a dynamic simulation, its uncertainty sample is calculated only once, in the initial time period.

Example: The following definitions model population changes over time:

Variable Population := Normal(30, 2)
Variable Birthrate := Normal(1.2, .3)
Time := 1 .. 10
Variable Pop_by_year := Dynamic(Population, Self[Time - 1] + Birthrate)

Chapter17 14.png


The uncertainty samples for Population and Birthrate are each calculated once, at the initial time period. The same samples are then used for each subsequent time period.

Resampling

If you want to create a new uncertainty sample for each time period (that is, resample for each time period), place the distribution in the last parameter of the Dynamic() function. For example, replace Birthrate with its definition in Pop_by_year:

Pop_by_year := Dynamic(Population, Self[Time - 1] + Normal(1.2, .3))

An alternative way to create a new uncertainty sample for each time period is to make Birthrate a dynamic variable:

Birthrate := Dynamic(Normal(1.2, .3), Normal(1.2, .3))
Pop_by_year := Dynamic(Population, Self[Time - 1] + Birthrate)

See Also

Comments


You are not allowed to post comments.