Time look up and variable look up

[mdsdoha]

Hi!

I need further understanding of time lookup and other variable related look up. I have attached a model where I have tried to use time look up. Could you please confirm and assure me whether this kind of lookup can be used in modelling?
My second question is that how can I develop a lookup where more than other two variable involved in a point. Such as capacity, target production, order's etc. I am totally lost about using x or y axis. moreover, I have seen some of the model used simple graph without using or mentioning any variable name. I have gone through help file along with proforma models but did not read well by me. Is there any simple writings to understand the things easy way with example.

Thanks

[Administrator]

You are nearly there with the lookups. See the attached model.

I've created a "lookup" called "Sales depot 1 table".

Then I've modified your "Sales depot 1" parameter so that it is now

Code: Select all

Sales depot 1 = Sales depot 1 table ( time )

[mdsdoha]

thanks. I understand your attached model but I have few questions in my mind. I have seen some model that they did not use any time variable. is it possible to continue the same purpose without giving input of time variable?

My second question, if I use "time to adjust" variable unit as "week" and will divide with an auxiliary variable which is unit/week, it will convert the unit as unit/week*week which is not logical? isn't it? what are the thumb rules of accepting unit such as 1/week, fraction/week, unit/week*week and so on?

My another question is regarding checking unit. why does the error comes like "used with dimensioned argument". what does it mean? how can i get rid of it?
Week

You are nearly there with the lookups. See the attached model.

I've created a "lookup" called "Sales depot 1 table".

Then I've modified your "Sales depot 1" parameter so that it is now

Code: Select all

Sales depot 1 = Sales depot 1 table ( time )

[Administrator]

I have seen some model that they did not use any time variable. is it possible to continue the same purpose without giving input of time variable?

Yes

My second question, if I use "time to adjust" variable unit as "week" and will divide with an auxiliary variable which is unit/week, it will convert the unit as unit/week*week which is not logical? isn't it?

Correct. unit/week/week makes no sense and would indicate an error in either model or units.

what are the thumb rules of accepting unit such as 1/week, fraction/week, unit/week*week and so on?

The rule for units is that they should be the same as what they are in reality. If you have something that is measured in percent/week, the units should be percent/week. If you have a delivery rate, that should be in units/week. As long as it makes sense, you model should pass the units check.

My another question is regarding checking unit. why does the error comes like "used with dimensioned argument". what does it mean? how can i get rid of it?

Turn off "warnings" and it will disappear. It's not an error, it is simply telling you that you are passing a dimensioned variable to the lookup which in this example, is fine.

[tomfid]

Actually, unit/week/week could make sense as a unit in some settings. For example, if you have a stock of capacity, measured in widgets/week, the flow of adding capacity would be in (widgets/week)/week.

[tomfid]

Also, for purposes of units checking, 1 = dmnl = dimensionless = fraction can be used interchangeably.

Another way to suppress the "dimensioned argument" warning is to suppress the units of the input with a converter, e.g.:

myvar = mylookup( time/unit time ) ~ dmnl
unit time = 1 ~ week

For data over time, best practice is to use data variables rather than lookups, if you can.

For other lookups, it's best practice to use dimensionless inputs and outputs, in order to avoid hidden assumptions. See Sterman's Business Dynamics http://amzn.com/007238915X for an example. Unfortunately you have to trade in a kidney to get a copy these days.

Tom

[mdsdoha]

Hi Tom

Thanks. In this case, do you mean that 1=week? is it right?

as you suggest me to practice data variable. could you please refer a simple data variable model where you called data from excel or some other places to run a model? please define how to use or locate input/output or X/Y variable if possible. Lastly, I have seen some model used "Subscript". I have gone through few model but failed to understand how it has been creates, what are its purpose? how it affects model variable? etc?

Thanks for your continuous support.

Also, for purposes of units checking, 1 = dmnl = dimensionless = fraction can be used interchangeably.

Another way to suppress the "dimensioned argument" warning is to suppress the units of the input with a converter, e.g.:

myvar = mylookup( time/unit time ) ~ dmnl
unit time = 1 ~ week

For data over time, best practice is to use data variables rather than lookups, if you can.

For other lookups, it's best practice to use dimensionless inputs and outputs, in order to avoid hidden assumptions. See Sterman's Business Dynamics http://amzn.com/007238915X for an example. Unfortunately you have to trade in a kidney to get a copy these days.

Tom

[Administrator]

as you suggest me to practice data variable. could you please refer a simple data variable model where you called data from excel or some other places to run a model? please define how to use or locate input/output or X/Y variable if possible.

It's all in the help system, see
http://www.vensim.com/documentation/ind ... f_data.htm

Lastly, I have seen some model used "Subscript". I have gone through few model but failed to understand how it has been creates, what are its purpose? how it affects model variable? etc?

Your profile states that you are using PLE, subscripts are not available in PLE.

[mdsdoha]

Dear Admin

As you referred me to read a link regarding data using in vensim was not understandable to me. Is it possible to get some link where "step by step" process has been written regarding get data from other sources in Vensim?

Secondly, I have purchased vensim professional. I am wondering how it shows to you as PLE? I am using Vensim 6.0.0.1 version. Could you please help me regarding subscript input in a variable?

thanks

as you suggest me to practice data variable. could you please refer a simple data variable model where you called data from excel or some other places to run a model? please define how to use or locate input/output or X/Y variable if possible.

It's all in the help system, see
http://www.vensim.com/documentation/ind ... f_data.htm

Lastly, I have seen some model used "Subscript". I have gone through few model but failed to understand how it has been creates, what are its purpose? how it affects model variable? etc?

Your profile states that you are using PLE, subscripts are not available in PLE.

[mdsdoha]

Dear Admin

As you referred me to read a link regarding data using in vensim was not understandable to me. Is it possible to get some link where "step by step" process has been written regarding get data from other sources in Vensim?

Secondly, I have purchased vensim professional. I am wondering how it shows to you as PLE? I am using Vensim 6.0.0.1 version. Could you please help me regarding subscript input in a variable?

thanks

as you suggest me to practice data variable. could you please refer a simple data variable model where you called data from excel or some other places to run a model? please define how to use or locate input/output or X/Y variable if possible.

It's all in the help system, see
http://www.vensim.com/documentation/ind ... f_data.htm

Lastly, I have seen some model used "Subscript". I have gone through few model but failed to understand how it has been creates, what are its purpose? how it affects model variable? etc?

Your profile states that you are using PLE, subscripts are not available in PLE.

[mdsdoha]

Dear Admin

As you referred me to read a link regarding data using in vensim was not understandable to me. Is it possible to get some link where "step by step" process has been written regarding get data from other sources in Vensim?

Secondly, I have purchased vensim professional. I am wondering how it shows to you as PLE? I am using Vensim 6.0.0.1 version. Could you please help me regarding subscript input in a variable?

thanks

as you suggest me to practice data variable. could you please refer a simple data variable model where you called data from excel or some other places to run a model? please define how to use or locate input/output or X/Y variable if possible.

It's all in the help system, see
http://www.vensim.com/documentation/ind ... f_data.htm

Lastly, I have seen some model used "Subscript". I have gone through few model but failed to understand how it has been creates, what are its purpose? how it affects model variable? etc?

Your profile states that you are using PLE, subscripts are not available in PLE.

[Administrator]

What format is your data in? Is it in Excel, text files or something else?

Subscripts: These allow you to replicate model structure quickly. For example, if you have a model that looks at bank balance, you could add subscripts to this so that it modelled many bank balances. The following section in the help has an example of a model with subscripts.
http://www.vensim.com/documentation/ind ... ?mgu06.htm

Let me know what format your data is in and I will be able to advise on how best to get it into Vensim.

Hope this helps.

Tony.

[mdsdoha]

Thanks for your reply.

I want to use data for two of the following reason and data is in excel format. I can convert other format if it is easy!

1. I want to use data for creating look up which will be input of a variable or output of a variable. such as last 52 weeks production, sales, demand, supply etc.

2. Yes, something like your example of bank. Say, if a firm manage multiple bank loan then it will increase the production or scope of the firm. how can I do this? Say, several things involved with one input such as calamities which decrease the business, bank loan which increase the business, low demand decrease the business. How can I build or create a combined multiplier?


I am not sure whether I can define it right way or not. If you do not understand what I am trying to do, please get back to me again. thanks a lot.

What format is your data in? Is it in Excel, text files or something else?

Subscripts: These allow you to replicate model structure quickly. For example, if you have a model that looks at bank balance, you could add subscripts to this so that it modelled many bank balances. The following section in the help has an example of a model with subscripts.
http://www.vensim.com/documentation/ind ... ?mgu06.htm

Let me know what format your data is in and I will be able to advise on how best to get it into Vensim.

Hope this helps.

Tony.

[Administrator]

1. I want to use data for creating look up which will be input of a variable or output of a variable. such as last 52 weeks production, sales, demand, supply etc.

See http://www.vensim.com/documentation/ind ... s_data.htm
There is an example model as well that you can look at.

2. Yes, something like your example of bank. Say, if a firm manage multiple bank loan then it will increase the production or scope of the firm. how can I do this? Say, several things involved with one input such as calamities which decrease the business, bank loan which increase the business, low demand decrease the business. How can I build or create a combined multiplier?

Read through the following. This is an example in adding subscripts to a model.
http://www.vensim.com/documentation/ind ... ?mgu06.htm

[tomfid]

The version number doesn't distinguish the type of Vensim you're using. There's a PLE 6.0a, DSS 6.0a, etc. The functionality available depends on whether you're using PLE, PLE Plus, Pro, or DSS.

[LAUJJL]

joined a way to deal with multipliers.
JJ

[mdsdoha]

Hi Tom

We have purchased 5.11 first then updated in to 6.0. Yesterday, I have successfully updated into 6.0A. I am very much sure that my version has this option of subscript.

The version number doesn't distinguish the type of Vensim you're using. There's a PLE 6.0a, DSS 6.0a, etc. The functionality available depends on whether you're using PLE, PLE Plus, Pro, or DSS.

[mdsdoha]

Hi LAUJJL

Thanks for your model. I want to develop something like that. Can you please explain your model in qualitatively so that I can understand how it functioning?
please!


thanks

joined a way to deal with multipliers.
JJ

[LAUJJL]

Hi

Suppose that you manage a business product whose turnover depends on three factors : size of the market (small, medium,high), overall quality of the product (small, medium,high) and the level of the competition (small, medium,high) and in the future these factors are susceptible to change and you can estimate the influence of each combination of these factors (27) on a standard turnover.
You will build a matrix of the 27 combined influences and use the model.

In the model joined the first factor is low, the second factor is medium and the third is high:
State of the system is 1,2,3.

When you run the model, the multiplier is equal to 1.4, which corresponds to the value of the matrix
Matrix(1,2,3).

It is too possible to get the values of the matrix using the vector elm map function but I find this formulation more transparent.

Regards.
JJ

[mdsdoha]

Thanks for your explanation. Do you have any idea, how we can get the information of subscript value? say, one firm is medium but doing good business, another is also medium but not doing good business. how can we differentiate them to put the value? Moreover, what could be the maximum value of a multiplier?

Hi

Suppose that you manage a business product whose turnover depends on three factors : size of the market (small, medium,high), overall quality of the product (small, medium,high) and the level of the competition (small, medium,high) and in the future these factors are susceptible to change and you can estimate the influence of each combination of these factors (27) on a standard turnover.
You will build a matrix of the 27 combined influences and use the model.

In the model joined the first factor is low, the second factor is medium and the third is high:
State of the system is 1,2,3.

When you run the model, the multiplier is equal to 1.4, which corresponds to the value of the matrix
Matrix(1,2,3).

It is too possible to get the values of the matrix using the vector elm map function but I find this formulation more transparent.

Regards.
JJ

[LAUJJL]

Hi

The minimum and maximum is either the result of available data or common sense and generally a mix of both.

If you have the chance to have data, use it, otherwise learn from experimenting with different scenarios.

SD is more a tool to think than to forecast and you have to think, not me and certainly not the model.

Regards.

JJ.

[mdsdoha]

Thanks a lot. I will try to follow your valuable comment.

Hi

The minimum and maximum is either the result of available data or common sense and generally a mix of both.

If you have the chance to have data, use it, otherwise learn from experimenting with different scenarios.

SD is more a tool to think than to forecast and you have to think, not me and certainly not the model.

Regards.

JJ.