Time bound

[mdsdoha]

Dear Experts

Hello

I am getting confused of using time bound. For example, I am using a lookup or Excel data as given input of say for 100 time bound. If I require to operate this model for more than 100; say 300 time bound or more, Vensim will take the last value of the data or lookup value consistently for above 100 time bound. To me, it is not realistic. How can I repeat the time based data even if I do not give input as data. Say, I have given input of 100 time bound data, in this case, if I will run this model for 200 time bound, how it will repeat same like as previous 100 or extrapolate based on given data.

Waiting for kind responses.

[Administrator]

There is lots in the help system for this. See

http://www.vensim.com/documentation/ind ... polate.htm
http://www.vensim.com/documentation/ind ... ?22820.htm
http://www.vensim.com/documentation/ind ... _trend.htm
http://www.vensim.com/documentation/ind ... recast.htm
http://www.vensim.com/documentation/ind ... ations.htm

[mdsdoha]

Thanks for your information. I have gone through all of them but can not replicate them in my model properly. It is happening due to my lack of knowledge. Do you have simplest example to go through? thanks

There is lots in the help system for this. See

http://www.vensim.com/documentation/ind ... polate.htm
http://www.vensim.com/documentation/ind ... ?22820.htm
http://www.vensim.com/documentation/ind ... _trend.htm
http://www.vensim.com/documentation/ind ... recast.htm
http://www.vensim.com/documentation/ind ... ations.htm

[Administrator]

Each one of the help links I gave you has an example model.

[mdsdoha]

Thanks for your continuous help. I have tried to replicate all of the example and found that the future graph either maintaining last point or growing up or down but not as like as similar like past data. Say, my sales is 10, 20, 40 20, 10, 20, 25, 15, 25, 20 and I want to predict what will happen at 2oth time step? I want that next 10 timestep will be replicate almost same trend of ups and down. Could anyone help?

Each one of the help links I gave you has an example model.

[tomfid]

You can use the MODULO function to get time to repeat. For example:

myvar = mylookup( MODULO(Time, repeatPeriod) )

[mdsdoha]

Hi Tom

Thanks for your reply. Does MoDULE produce multiplier?? I have tried all the day to incorporate this MODULE concept in a model to see, how it goes but failed. I am attaching a sample model where I have tried to link with the model. In this model, data has been entered for 104 weeks and I want to see 200 or more timestep(futuristic) but need to see the behavior as like as 104 data trend. Any help will be appreciated.

You can use the MODULO function to get time to repeat. For example:

myvar = mylookup( MODULO(Time, repeatPeriod) )

[tomfid]

It's a little hard to interpret this because there are no units on A MOD B or the lookup, but it looks to me like the usage is backwards. In effect, you have

A MODULO B = MODULO( A, RAMP(lookup(Time),INITIAL TIME,FINAL TIME) )

Assuming that A MOD B is an effect on demand, you want something like

A MOD B = lookup( MODULO( Time, repeat_period ))

Where "lookup" will be a history time series that repeats every repeat_period time units. It's not clear what your time unit is, because your lookup seems to have a discontinuity every 25 units (months?).

[mdsdoha]

I just tried to replicate proforma MUDULO model with my model. MAy be I failed to do so. What I want to do is that I have 104 weeks data and I want to see this 104 weeks data will replicate or show the almost same trend for another 200 weeks plus. Can you help to show me this in my model please?

It's a little hard to interpret this because there are no units on A MOD B or the lookup, but it looks to me like the usage is backwards. In effect, you have

A MODULO B = MODULO( A, RAMP(lookup(Time),INITIAL TIME,FINAL TIME) )

Assuming that A MOD B is an effect on demand, you want something like

A MOD B = lookup( MODULO( Time, repeat_period ))

Where "lookup" will be a history time series that repeats every repeat_period time units. It's not clear what your time unit is, because your lookup seems to have a discontinuity every 25 units (months?).

[LAUJJL]

Hi Msdoha

To solve your problem, build your models correctly.

1. To do so, first simplify your model to the extent that is only left your difficulty (seems to be lookup or/and modulo).

2. Spot all your supplementary variables and either erase them or write in the comment what it is calculated for.

3. Put comments on equations when necessary, for yourself and for others.

4. Split equations so that they only have preferably 3 or maximum 4 inputs. One of your equations has 6 inputs. It will be easier to understand the model and to check it.

5. Choose better and more significant names (avoid A B lookup modulo that have no real world meaning)

6. Correct unit errors.

7. Normalize your lookups. See normalize in the Vensim search documentation.

8. Check the variables not used as supplementary.

If you have done that, maybe you will not need any help for your problem and more important, for
other problems to come later on.

Regards
JJ

[Administrator]

I've put in two different methods in the attached model. Will one of these do?

[mdsdoha]

I really appreciate your help. It will help me a lot. Can you please explain that why did you use shift option? Is there any particular reason of using it?

Thanks again

I've put in two different methods in the attached model. Will one of these do?

[mdsdoha]

Dear Admin

Thanks for your proforma model. Could you please tell me how can I drain out something from MODULO. For example, we have set repeat time is 25 and will be added 25000 in each 25th time step. Now the problem is capacity of this firm is 75. it can not accommodate more than 75. this means, in third repeat it will overflow. Now, I want to drain out 25000 unit in every 50th time step. How can I do this? Thanks and waiting for your kind reply.


Doha

I've put in two different methods in the attached model. Will one of these do?

[Administrator]

Have a go at implementing it yourself, and if you have problems post the model and we'll take a look.

[mdsdoha]

Hi Dear

Here, I have attached a simple model. I have given input of Modulo Lookup where minimum input "321829" and maximum input "544121" in different 26 time step. When I am using modulo, it is replicating same after 26 time step but the problem is that it almost doubling the figure after a cycle of 26 or so. I want same replication whatever happened in 1-26, same will happen 27-52 time step. May be I am not far away but I could not make it.

Secondly, you have written the code of drain out the figure from level in every time step. I tried to drain out but it contain remain same figure in level as it is not completely draining out.

thanks and I appreciate your help.

Have a go at implementing it yourself, and if you have problems post the model and we'll take a look.

[Administrator]

Make the multiplier a constant with a value of 1.