Ventana software support forum

Thanks for the help - and it is so easy !

Hi, I have a requirement and a solution but I do not like it (and therefore I look for an improvement)! The requirement is, that a have to split a number (here: 1) randomly in several parts (here: 4) and the sum of all parts have to be the initial value. e.g.: 1 is splitted into 0.2 + 0.3 + 0.4 + 0....

Thanks,
just for your information:
Copy - paste helps me out. I adapt / expand my old model and can use new rate-symbols with the "old" dimension.

Greetings,
jmu

Hi,
very long time ago and with older vensim version I could change the size of the symbol that is used for a rate (you know: the "double triangle").

Now I fail - has this feature gone or do I miss something (I use Vensim PLE Plus, 5.10e)?

Regards,
jmu

Hi,
I am about to develop (do some experiments) some models about developement problems (mainly west africa, sahel region).

Is anyone out here who can me point so some already existings models (books, papers, sample models, whatsover)?

Any hint is appreciated!

Best regards
jmu

... hidden in your equations, there's no way to test them for sensitivity

That's an argument !!!!

Thanks,
jmu

Thanks for the discussion and your patience. Concerning X = X: Ok, but this allows me in advance to determine, if a stock variable will increase / decrease in the next time step. And when I use a delay I can simulate some adaption actions. But you already showed me a different way. Concerning the un...

What I wanted do add: The unit-problem with delay is still here (in other situations). The manuals says: Units: DELAY1(units,time) --> units If I understand it right then the output unit is the same as the input unit. But I always see the time unit involved. This bothers me and causes some unit chec...

Thanks for the help.

Meanwhile I come up with a different idea:

incrdecr = (sum of all inflows to content) - (sum of all outflows of content)

That should also work.

Thank you,
jmu

Hi, I have a stock variable named "Content" (unit "Euro") and want to know, if it currently increases or decrease. To calculate this I created a variable IncrDecr = Content-DELAY1(Content, 1) As far as I see IncrDecr is < 0, 0 or >0 as I need it. But what is the correct unit? I a...

thanks for the insights,
jmu

Hi, due to my lack of knowledge I run into a problem. Maybe someone could give my an advise. I have a stock variable A. There is one input (a constant!) and there are two outputs. The outputs depend on the value of A. A holds the amount the people from age 0 to age 9 (example). The input is a consta...

That's what I currently do - just looking for a built-in way

Thanks,
jmu

Hi,
is it possible to create spider diagrams with Vensim (PLE)?

If you don't know what I mean, here are some examples:
http://www.kstoolkit.org/Spider+Diagrams
http://www.niwotridge.com/images/BLOGIm ... iagram.jpg

Thanks a lot,
jmu

I cannot find "System Dynamics Modeling by R.G. Cole" at Amazon?" Please give us more details about this book!

Thanks,
jmu

What I forgot to mention: http://www.public.asu.edu/~kirkwood/sysdyn/VenPLE.pdf This is a short introduction in Vensim PLE My advise: Download the molecules from Vensim, install it - you will find a PDF in the installation directory and study it. Molecules are basicly small models that can be copied...

Hi,
maybe this helps:
http://www.public.asu.edu/~kirkwood/sys ... DIntro.htm

Here you can find some sample models:
http://www.metasd.com/models/index.html#Business


Regards,
jmu

Thanks, that helps.

BTW: I always use units and constants. I just wanted to make it clear without lots of typing.

Concerning molecules: as a beginner I am still a little bit lost here.

jmu

Hi, this question is not Vensim specific but because I use Vensim there might be a build in function (which I could not find) that helps me out ... I have a calculated variable (let's say "amount-of-food") that should be distrubuted to some other variables (let's say "food-for-animal-...

Thanks for your answer - I see how much I still have to learn .... But the problem was completly different. I really wondered about the drop below zero in my small model (it was just a single value at the second step). But when I switch from Euler to Runge-Kutta then everything works as expected. A ...

Hi, a beginner's problem. I have a stock variable which has 2 outflows. Now I want to make sure that the stock never reaches something below zero. stock ... population outflow 1 ... moveing outflow 2 ... deaths Both outflows are influced by some other varibales. What I have done is this: for both ou...