Hello, I have animals that die at several points during the year. At a certain time each year, I need to sum up these deaths from over the previous 365 days in order to estimate how many animals are required to replace them. How do you suggest that I find this number? I am not using the death total as a Level per se, and directly feeding it into the replacements via a flow (as I might not have enough animals ready), but I am using it as a target number to inform the real number of replacements I should try to produce.
Thank you.
accumulate auxillary values
-
- Super Administrator
- Posts: 4590
- Joined: Wed Mar 05, 2003 3:10 am
Re: accumulate auxillary values
You accumulate them using a level, then reset the level at the end of the year (or at some other point such as when the animals are replaced).
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
Re: accumulate auxillary values
You can use a stock to keep track of this. Make the inflow the current death rate, and the outflow equal to a DELAY FIXED of the same rate, with a time constant of one year (in whatever units your model is using).
/*
Advice to posters (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Blog: http://blog.metasd.com
Model library: http://models.metasd.com
Bookmarks: http://delicious.com/tomfid/SystemDynamics
*/
Advice to posters (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Blog: http://blog.metasd.com
Model library: http://models.metasd.com
Bookmarks: http://delicious.com/tomfid/SystemDynamics
*/
Re: accumulate auxillary values
Thank you, producing a level with a delayed outflow worked great.
Re: accumulate auxillary values
What you choose depends on what you need to represent - if you're modeling an accounting process explicitly, the pulsed or delayed reporting stock is good. If you're just capturing the natural delay and smoothing in a perception process, it's much simpler to use a SMOOTH or SMOOTH3 function.
/*
Advice to posters (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Blog: http://blog.metasd.com
Model library: http://models.metasd.com
Bookmarks: http://delicious.com/tomfid/SystemDynamics
*/
Advice to posters (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Blog: http://blog.metasd.com
Model library: http://models.metasd.com
Bookmarks: http://delicious.com/tomfid/SystemDynamics
*/