Making Connections - Latest Comments

Re: Private: Modeling Customers Switching Between Brands – The General Case

kchichakly — Tue, 16 Apr 2013 10:47:33 -0000

Good question. New people arrive through the gaining customers inflow. To add 100 more for brand A at a certain time (let's use month 5 for the example), you would change that formula as follows:

market_share[Products]*customer_influx + (Products = 1)*PULSE(100, 5, 10000)

[For version 9, use (ARRAYIDX() = 1) instead of (Products = 1).]

However, I do not think this is quite what you are looking for because the market shares/switching percentages are constant, so the model will still seek the distribution given in those switching constants.

To make the model dynamically vary the brand switching based on some criteria, you have to turn the constants in the table into equations for your new formulation. For example, you can use STEP to reduce A's switching out probability at a certain time, and/or adjust market share (second model). Using the second model, you could adjust only the market share to show an increase in both new customers and switching customers choosing brand A (rather than using the PULSE above). Just make sure to adjust your equations so that the sum of the market shares is always one.

While stepping up the market share or pulsing in extra customers can be an interesting policy exercise or model sensitivity test, you normally would tie these probabilities and market shares to dynamically changing endogenous variables of the model, such as price, features, reputation, perception of value, etc.

Re: Private: Modeling Customers Switching Between Brands – The General Case

Mam — Sat, 13 Apr 2013 02:38:22 -0000

How do you change the matrix if there is category expansion. Eg, in time 0, there were 500 people in market and now 600. Especially if we know that new 100 people are buying brand A.

Re: What is the difference between STELLA and iThink?

Anonymous — Tue, 22 Jan 2013 21:00:58 -0000

Difference at initial configurations could be handled as some default profiles beside user defined ones. It seems there should be other reasons for releasing and maintaining two different versions of the same product. Working on concepts and outsourcing software production will improve the product since at 2013 it seems like 1995 soft-wares...

Re: Private: Working with Array Equations in Version 10

Cam — Mon, 31 Dec 2012 20:17:06 -0000

I agree with showing actual example that can be downloaded

Re: Private: Working with Array Equations in Version 10

pedrodago — Sun, 23 Dec 2012 01:12:53 -0000

This article seems very interesting, but I suggest it would be better to develop examples based on stock and flow diagrams which present real situations.

Above all do more examples of using arrays in conveyor and queues.

Anyway congratulations for having written this.

Merry Christmas from Monterrey, Mexico.

Re: Private: Working with Array Equations in Version 10

Pedro Dagoberto Almaguer Prado — Sun, 23 Dec 2012 01:08:38 -0000

This article seems very interesting, but I suggest it would be better to develop examples based on stock and flow diagrams which present real situations.

Above all do more examples of using arrays in conveyor and queues.

Anyway congratulations for having written this.

Merry Christmas from Monterrey, Mexico.

Pedro Almaguer Prado pedrodago@gmail.com

Re: Tip: Setting up imports for 2D Graphical Functions

sigmund — Mon, 17 Dec 2012 02:41:58 -0000

If there are more than 2000 projects, project 1, project 2,..., project 2000. I want to use 1001, 1002,..., 3000 instead of project 1, project 2, .... Is there any method to import them from excel, or is there any function to set them in stella? Thank you.

Re: Matrix Arithmetic

kchichakly — Sun, 16 Dec 2012 13:59:26 -0000

These files are all ITM files, i.e., created by iThink. STELLA will open them if you choose "iThink doc" from the pop-up menu at the bottom of the Open File dialog.

Re: Matrix Arithmetic

kchichakly — Sun, 16 Dec 2012 13:56:52 -0000

This is trickier than the other way, but still not difficult. Say d is the vector and I want to put it into the diagonal of square matrix a. In version 9.1.5 or earlier, make the a's equation:

IF ARRAYIDX() = ARRAYIDX(2) THEN d[Dim3] ELSE 0

In version 10, make a's equation:

IF @1 = @2 THEN d[Dim3] ELSE 0

Re: Matrix Arithmetic

Noé Aron fuentes — Mon, 10 Dec 2012 23:38:11 -0000

How I convert a vector to a diagonal matrix ?

Re: Private: What are “Mental Models”?

Camilia Moussawi Khanafer — Sun, 02 Dec 2012 09:48:14 -0000

not bad at all

Re: Private: Modeling Customers Switching Between Brands – The General Case

kchichakly — Mon, 26 Nov 2012 14:00:38 -0000

This shows a way to model the effect of customers changing brands, presumably through consumer preferences and competition. It is explicitly looking at number of customers, not how much each customer is spending. As such, contraction in spending is outside the bounds of this model. However, once you know how many customers you have, you can multiply that by the average spend per customer per month to get your monthly revenue. In a contraction, the average spend per customer would drop based on some function you provide (using the STEP or RAMP functions or your own graphical function). You may also lose customers in a contraction, which you would implement by increasing the loss rate in the model above. It is likely during a contraction that you would also have a reduction in the customer influx.

Re: Private: Steady-State Initialization of Conveyors

valentina — Tue, 20 Nov 2012 03:43:50 -0000

why it can only be used one leakage for conveyor?, isn't it probable for a conveyor to have more than one?

Re: Private: Integration Methods and DT

kchichakly — Thu, 15 Nov 2012 22:49:50 -0000

DT, as we use it in our models, is short for delta time, i.e., the difference between two time values. It is NOT the dt from calculus (as pointed out above). The difference between two time values has the same units as the time values being subtracted, i.e., time. DT has the same units as the unit of time you set in the run specs.

Re: Tip: Setting up imports for 2D Graphical Functions

robert — Tue, 18 Sep 2012 17:30:50 -0000

If i have a model that i want to run repetitively (like a 100 times) with a different set of random numbers, how can this be done? I was thinking of having a counter for the repetition i am in, I then I can look in the 10th or 12th coloumn for my set of random numbers. Really do not want to hard code this... Thanks so much for your help.

Re: Using PEST to Calibrate Models

Dinmech — Fri, 10 Aug 2012 08:18:28 -0000

@kchichakly I found the main issue was windows 2007 ; i am working in it. In PEST manual also suggest the same. Sometime batch files works well alone in dos mode, mosttimes is not and doesnt shows the errors. Rarely it works in pst files, but it couldnt open the template and instruction files (its a error). I dont know hw to fix this bug!?!?!??! do u have any suggestion?

Re: Using PEST to Calibrate Models

Dinmech — Fri, 10 Aug 2012 04:04:32 -0000

Hi kchichakly, Thanks for your comments. I solved this problem. But new problem arised, if i run batch file (test.bat) alone, it updates the model output files. when i am using pest filename for running the model, it shows the error "Unexpected end to model output file OBSPOINTS.OUT.
Instruction line follows -
"l3 @TEMP@"
After this error-All the model ouput files has been erased. my email id is dinkuleuven@gmail .com. u can email if possible, so i can send my files to check.

Thanks

Regards

Dinesh

Re: Using PEST to Calibrate Models

kchichakly — Thu, 09 Aug 2012 12:20:04 -0000

Hi Dinmech, this tells you there is an error in your PST file. If you look at the sample, you will notice that there is a "* model command line" section near the end that needs a command line after it (I invoke a batch file in the example). PESTGEN will create this file for you and then you should just have to make minor edits. Do not accidentally delete things or change the spacing. It is very finicky. Please refer to the PEST manual if you cannot follow the PST file format.

Re: Using PEST to Calibrate Models

Dinmech — Thu, 09 Aug 2012 06:28:12 -0000

VS2DHP.PST should read Derivatives command line or model command line - error message....wht it mean??/

Re: Cleaner Vehicles through Fees & Rebates

Søgemaskineoptimering — Wed, 08 Aug 2012 12:29:07 -0000

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Re: Published Papers that Feature Models

Patrickhenry — Mon, 11 Jun 2012 17:43:10 -0000

In the same way can someone help me with developing graph, as the attached image. Any help would be greatly appreciated.

Looking forward for the help.

Thank you.

Re: Published Papers that Feature Models

Patrick — Mon, 11 Jun 2012 17:31:02 -0000

patrick

Re: Private: Converting a Sector-based Model to Modules

Sdavie — Thu, 07 Jun 2012 12:04:42 -0000

After ghosting and entity within one module close the module, open the next module and drop the ghosted entity. Both modules do not need to be open at the same time. Please e-mail support@iseesystems.com if you have questions.

Re: Private: Converting a Sector-based Model to Modules

Sikander — Wed, 06 Jun 2012 17:07:34 -0000

Does this method work for 9.1.4 or has been written for some earlier version? I cannot open one module if the other is open to paste a ghost, even when I go up one level.

Re: Private: Steady-State Initialization of Conveyors

Sdavie — Fri, 18 May 2012 17:25:50 -0000

We will reply to this request in e-mail.