Have you checked the example in the Help system, Ch. 4, Reference Manual, functions?
ALLOCATE AVAILABLE isn't designed for many-to-many situations (Relays -> Collects) so the behavior you're getting sounds right. I think we need to debug your FIND MARKET PRICE version.
Search found 3811 matches
- Tue Mar 27, 2012 2:56 pm
- Forum: Vensim
- Topic: Over Allocation
- Replies: 4
- Views: 4128
- Mon Mar 26, 2012 11:11 pm
- Forum: Vensim
- Topic: ODBC Problems (Connecting Vensim to MS Access)
- Replies: 8
- Views: 7572
Re: ODBC Problems (Connecting Vensim to MS Access)
This is great. I posted it to a few places. http://blog.metasd.com/2012/03/vensim-data-with-odbc/ http://www.facebook.com/pages/Vensim/131233120248692 Thanks!
- Mon Mar 26, 2012 5:57 pm
- Forum: Vensim
- Topic: Kernel density estimation
- Replies: 8
- Views: 4120
Re: Kernel density estimation
OK. I think my example should work for you.
- Mon Mar 26, 2012 4:34 pm
- Forum: Vensim
- Topic: Kernel density estimation
- Replies: 8
- Views: 4120
Re: Kernel density estimation
Here's an example:
I haven't double checked to be sure that the resulting pdf integrates to 1, but it should be OK.- Mon Mar 26, 2012 3:34 pm
- Forum: Vensim
- Topic: Kernel density estimation
- Replies: 8
- Views: 4120
Re: Kernel density estimation
OK - I think this is actually fairly easy. I'll post an example. One more question though: once you have the kernel-smoothed density, what will you do with it? For example, do you want to pick arbitrary points from it, or generate incomes at uniformly-spaced levels, essentially using the pdf as an i...
- Mon Mar 26, 2012 1:29 pm
- Forum: Vensim
- Topic: error messages related to lookups
- Replies: 10
- Views: 11708
Re: error messages related to lookups
Specifically, see:
http://www.vensim.com/documentation/fn_lookup_area.htm
There's a chapter in the User's Guide on lookups:
http://www.vensim.com/documentation/usr08.htm
For iThink users, the WITH LOOKUP syntax may be more familiar:
http://www.vensim.com/documentation/fn_with_lookup.htm
http://www.vensim.com/documentation/fn_lookup_area.htm
There's a chapter in the User's Guide on lookups:
http://www.vensim.com/documentation/usr08.htm
For iThink users, the WITH LOOKUP syntax may be more familiar:
http://www.vensim.com/documentation/fn_with_lookup.htm
- Sun Mar 25, 2012 6:19 pm
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
It's using the profile and the delay time together to normalize the pdf and establish the mean time. Off the top of my head, I believe that the procedure is (a) integrate x*lookup(x) over the range of the lookup, and divide by the range, to determine the mean arrival time in the lookup (b) rescale t...
- Sun Mar 25, 2012 2:18 am
- Forum: Vensim
- Topic: error messages related to lookups
- Replies: 10
- Views: 11708
Re: error messages related to lookups
Vensim differs from iThink in that a lookup can be used in more than one place, so the lookup table is separate from the input and expressions that use the input. In that respect it is more like DYNAMO. In DYNAMO you might write: FCAOR = TABHL( FCAORT, NRFR, 0, 1, .1 ) FCAORT = 1/.9/.7/.5 ... (borro...
- Sat Mar 24, 2012 5:26 pm
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
Incidentally, if there's some other software you use that does things differently/better, we're always interested to hear about it.
- Sat Mar 24, 2012 5:25 pm
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
I'll take a look. If you don't need 'init' and 'init grow' you can set them to 0. The profile and delay time parameters work together. The profile gives the shape of the distribution. It's then scaled so that (a) the area under the curve is 1 and (b) the mean arrival time is equal to the delay time ...
- Sat Mar 24, 2012 4:28 pm
- Forum: Vensim
- Topic: Kernel density estimation
- Replies: 8
- Views: 4120
Re: Kernel density estimation
Are you trying to smooth across time, or income values, or both?
If this is all you're doing, you'd be better off using a stats package. But if this is part of a dynamic model, we can probably come up with a strategy that works.
Tom
If this is all you're doing, you'd be better off using a stats package. But if this is part of a dynamic model, we can probably come up with a strategy that works.
Tom
- Sat Mar 24, 2012 4:24 pm
- Forum: Vensim
- Topic: error messages related to lookups
- Replies: 10
- Views: 11708
Re: error messages related to lookups
You need to pass an argument to your lookups, as in y = lookup(x)
You might take a look at the "LOOKUP functions.mdl" example in the help system, Reference Manual, Chapter 4, particularly the 'price with normal LOOKUP usage' variable.
You might take a look at the "LOOKUP functions.mdl" example in the help system, Reference Manual, Chapter 4, particularly the 'price with normal LOOKUP usage' variable.
- Thu Mar 22, 2012 8:19 pm
- Forum: Vensim
- Topic: Problem with PULSE TRAIN
- Replies: 2
- Views: 2106
Re: Problem with PULSE TRAIN
Set your width parameter to TIME STEP/2 rather than 0, and this should work.
- Thu Mar 22, 2012 8:10 pm
- Forum: Vensim
- Topic: C Compiled vensim programs
- Replies: 2
- Views: 2197
Re: C Compiled vensim programs
If you're running compiled simulations, Vensim creates a .dll in the same directory as your model.
See also http://blog.metasd.com/2011/06/setting- ... n-windows/
See also http://blog.metasd.com/2011/06/setting- ... n-windows/
- Thu Mar 22, 2012 3:38 pm
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
OK, here's an example, based on the one in the help system: DELAY PROFILE+.mdl I created an arbitrary Weibull-ish profile in the lookup. If you set the 'pulse install rate' and 'historic install rate' to 0, and the 'constant install rate' to some value, you can see that you get the expected Little's...
- Thu Mar 22, 2012 2:58 pm
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
The initial growth rate parameter specifies the trajectory of your appliance installation rate f(t) prior to the start of the model (INITIAL TIME).
I'll see if I can cook up an example.
I'll see if I can cook up an example.
- Wed Mar 21, 2012 9:12 pm
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
Got it. The simple way to do this is with DELAY PROFILE (see the example in Ch. 4 of the Reference Guide). The lookup argument to DELAY PROFILE is the distribution of the wait or residence time of the material (scaled by the delay time parameter). Unfortunately there isn't any easy way to parametric...
- Wed Mar 21, 2012 3:59 am
- Forum: Vensim
- Topic: how to perform a convolution in vensim
- Replies: 17
- Views: 12835
Re: how to perform a convolution in vensim
A general convolution is acausal, i.e. values at a point in time may use information from the future. We don't generally support acausal modeling, though there are technical tricks for accomplishing it in some cases.
If you say more about your problem we might have a solution.
If you say more about your problem we might have a solution.
- Wed Mar 21, 2012 3:57 am
- Forum: Vensim
- Topic: Kernel density estimation
- Replies: 8
- Views: 4120
Re: Kernel density estimation
The short answer is yes.
However, there aren't any tools for this specific purpose, so it's up to you to develop and equation structure and optimization control file that will get the job done.
If you say a bit more about what you're trying to do, we may be able to be more helpful.
However, there aren't any tools for this specific purpose, so it's up to you to develop and equation structure and optimization control file that will get the job done.
If you say a bit more about what you're trying to do, we may be able to be more helpful.
- Wed Mar 21, 2012 3:55 am
- Forum: Vensim
- Topic: Vensim Query (Stocks and Flows)
- Replies: 1
- Views: 1481
Re: Vensim Query (Stocks and Flows)
Multiple flows in/out of a stock are fine. You may find that you'll need multiple stocks as well - for example, a separate stock and associated flows for high and low value customers. There's quite a bit of tutorial material in the User Guide and Model Guide in the help system. We're working on gett...
- Tue Mar 13, 2012 11:26 pm
- Forum: Vensim
- Topic: Vensim and Digest
- Replies: 6
- Views: 6215
Re: Vensim and Digest
I'd just run through the text and look for unusual functions, though it could be something as simple as an IF THEN ELSE. Any discrete behavior will wreak havoc on the linearlization of the model, I'd guess. Also look for any variable names that incorporate special characters and therefore require &q...
- Tue Mar 13, 2012 1:39 am
- Forum: Vensim
- Topic: WARNING:delay requiring more than 5000 levels
- Replies: 1
- Views: 1568
Re: WARNING:delay requiring more than 5000 levels
Your delay implies 52/.0078125 = 6656 discrete levels, hence the warning. It's possible that this is necessary, but 6656th order delays aren't exactly common. We'd have to know more about your model to know whether this is sensible or not.
- Sun Mar 11, 2012 3:25 pm
- Forum: Vensim
- Topic: ODBC Problems (Connecting Vensim to MS Access)
- Replies: 8
- Views: 7572
Re: ODBC Problems (Connecting Vensim to MS Access)
Hmm ... that should be fine then. I'll do some testing to be sure everything is working right.
Tom
Tom
- Thu Mar 08, 2012 2:42 pm
- Forum: Vensim
- Topic: ODBC Problems (Connecting Vensim to MS Access)
- Replies: 8
- Views: 7572
Re: ODBC Problems (Connecting Vensim to MS Access)
Glad you worked it out. I'm guessing that your copy of Vensim is not the latest; .vdi files should work in the pre-processing step, but there was a bug in the dialog processing that prevented that, fixed fairly recently (5.11). Putting the .vdi in the Changes field as you did is a valid solution tho...
- Mon Mar 05, 2012 5:41 pm
- Forum: Vensim
- Topic: Vensim's confidence interval estimation (likelihood ratios)
- Replies: 10
- Views: 8514
Re: Vensim's confidence interval estimation (likelihood rati
I just checked some old correspondence, and the issue is not what I was thinking of. Gokhan is correct that there is a difference; the origin is reporting conventions rather than a technical error. Here's an attempt at an explanation. Suppose you have a model with parameters a that you're fitting to...