Search found 112 matches

by nikvyas
Fri Dec 14, 2007 9:53 am
Forum: Vensim
Topic: How to convert a pulse of magnitude (x), width 1 into a puls
Replies: 7
Views: 3427

Thanks Bob. Unfortunately it doesn't really work very well, so I've decided that the best option is to change the structure of the model, so that the pulses are now elements of a subscript and I've ensured that the pulses in each element have no chance of "running" into each other. I then ...
by nikvyas
Wed Dec 12, 2007 8:30 am
Forum: Vensim
Topic: How to convert a pulse of magnitude (x), width 1 into a puls
Replies: 7
Views: 3427

Thanks Bob...................although I'm really struggling to understand the equations I'm afraid. Could you please let me know the equation for "ouput by input" please (maybe you could attach a tiny model ;) )?

Thanks

Nik

[Edited on 12-12-2007 by nikvyas]
by nikvyas
Tue Dec 11, 2007 1:17 pm
Forum: Vensim
Topic: How to convert a pulse of magnitude (x), width 1 into a puls
Replies: 7
Views: 3427

Thanks Bob - however..................................... The following situation isn't captured in your equations (where pulses close together will add up): convert: input= 5002004602000060000000 into: output:111220122321101111100 i.e. - if you consider each of the pulses in "input" to be...
by nikvyas
Tue Dec 11, 2007 9:27 am
Forum: Vensim
Topic: How to convert a pulse of magnitude (x), width 1 into a puls
Replies: 7
Views: 3427

How to convert a pulse of magnitude (x), width 1 into a puls

Good morning Bob, JJ, all. I have another query that I'd be very grateful to have some assistance with. I have a function that has created a series of pulses of varying heights. What I need to do is to convert these pulses of height (x) into pulses of width (x). For instance: convert: input= 5000000...
by nikvyas
Fri Dec 07, 2007 1:48 pm
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

Thanks a lot Bob and JJ - I've got exactly what I needed.

After using Vensim for almost two years................I've finally been converted to the beauty of subscripts!
by nikvyas
Fri Dec 07, 2007 10:00 am
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

Hi JJ. Thanks very much for your reply. I've tried your suggestion, but it doesn't seem to work unfortunately. I'd be grateful if you (or Bob) could have a look at the attached (very simple) model and let me know what I'm doing wrong. I also have another, hopefully simple, question - I promise it'll...
by nikvyas
Thu Dec 06, 2007 2:30 pm
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

Thanks Bob - however the problem (as i see it) is that arrays (or subscripts) cannot contain variables. As far as I was aware, you had to explicitly define the elements; i.e: array1[ftype]=1,2,3,4,5,6,7,8,9,10 But all of the elements in my array will be variables. i.e., array1[ftype]=repair_length1,...
by nikvyas
Thu Dec 06, 2007 2:03 pm
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

But actually my main problem at the moment is in the sorting. I'm not sure that VECTOR SORT will do the trick. As the equation above shows, I need to sort the repair schemes in order of repair length. But I also need to conserve the relationship between the repair length and its associated probabili...
by nikvyas
Thu Dec 06, 2007 12:55 pm
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

Hi Bob. Maybe I explained it wrongly. When an a/c lands, it has a number of arisings and it is the arising that takes the longest time to fix that determines the downtime of the a/c - so the greater the number of arisings, the higher is the probability that one of the arisings will take a long time ...
by nikvyas
Thu Dec 06, 2007 9:52 am
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

Thanks Bob. I've downloaded the latest version (5.7) and can see the Vector Lookup function. However, the instructions for its use are somewhat confusing. I'd be very grateful if you could spend a couple of minutes in helping me out of my little problem. What I want to do is as follows: I have ten r...
by nikvyas
Fri Nov 30, 2007 8:35 am
Forum: Vensim
Topic: Lookup Tables and Variables
Replies: 11
Views: 4933

Lookup Tables and Variables

Good morning all.

I was wondering if it's possible to have the elements of a lookup table as variables? i.e., rather than have defined, constant elements like:

[(0,0)-(10,10)],(1,4),(2,8),(3,9),(4,10)

have instead:

[(0,0)-(10,10)],(1,var1),(2,var2),(3,var3),(4,var4)

Thanks in advance.
by nikvyas
Thu Feb 08, 2007 9:06 am
Forum: Vensim
Topic: Bug? With The Random Uniform Function
Replies: 4
Views: 2591

Thanks Bob - I've emailed the model.

The password is:

ziggyzag

[Edited on 2-8-2007 by nikvyas]
by nikvyas
Wed Feb 07, 2007 1:46 pm
Forum: Vensim
Topic: Bug? With The Random Uniform Function
Replies: 4
Views: 2591

Thanks Bob - however that doesn't seem to be the problem. I have now amended my model, so that all of the seeds are now seperate (i.e., there is no global seed) - and still, if I alter a variable elsewhere in the model, the random numbers also change! I can't post the model on this forum, but is the...
by nikvyas
Tue Feb 06, 2007 9:48 am
Forum: Vensim
Topic: Bug? With The Random Uniform Function
Replies: 4
Views: 2591

Bug? With The Random Uniform Function

Good morning all. I've built a complex model and recently did sensitivity analysis on it. However, the results weren't entirely as expected. On further investigation, I found the following: random=RANDOM UNIFORM( 0 , 1 , overall seed ) PI177=IF THEN ELSE( RANDOM UNIFORM( 0 , 100 , overall seed ) <=&...
by nikvyas
Wed Dec 13, 2006 11:50 am
Forum: Vensim
Topic: More pulse queries.
Replies: 5
Views: 3030

Hi JJ.

yes - we have the Pro version (recently ordered three more copies). I've tried to avoid using subscripts up till now, because I found it to complicate matters further. However, I'm sure that after getting used to them, they will be a great help.

Thanks

Nik
by nikvyas
Fri Dec 08, 2006 2:49 pm
Forum: Vensim
Topic: More pulse queries.
Replies: 5
Views: 3030

Sorry JJ - you are quite right.
by nikvyas
Tue Dec 05, 2006 3:14 pm
Forum: Vensim
Topic: More pulse queries.
Replies: 5
Views: 3030

More pulse queries.

...

[Edited on 12-8-2006 by nikvyas]
by nikvyas
Wed Nov 29, 2006 8:38 am
Forum: Vensim
Topic: Randomly sampling pulses.
Replies: 3
Views: 2225

Thanks a lot Bob.
by nikvyas
Mon Nov 27, 2006 11:53 am
Forum: Vensim
Topic: Randomly sampling pulses.
Replies: 3
Views: 2225

Do you guys think the following approach is OK? variable=RANDOM EXPONENTIAL( 0 , 1 , 0 , 0.5 , 1234 ) filtered=IF THEN ELSE( variable<=0.5,"pulses1",0) So, if I only want 40% of pulses to go through, I can just alter the equation to: filtered=IF THEN ELSE( variable<=0.4,"pulses1"...
by nikvyas
Mon Nov 27, 2006 11:32 am
Forum: Vensim
Topic: Randomly sampling pulses.
Replies: 3
Views: 2225

Randomly sampling pulses.

Good morning all. I was wondering if somebody could help with the following conundrum. I have a series of non-uniform, non-random pulses throughout a year (called "pulses1"). I want to filter this series so that, for instance, half continue to be a pulse (value 1) wheras the other half bec...
by nikvyas
Thu Nov 23, 2006 10:52 am
Forum: Vensim
Topic: if demand is a distribution
Replies: 7
Views: 4545

There is already a function for Normal distribution (as well as other distributions) called RANDOM NORMAL
by nikvyas
Thu Nov 23, 2006 8:29 am
Forum: Vensim
Topic: new problem
Replies: 18
Views: 7797

Thanks Bob.
by nikvyas
Mon Nov 20, 2006 8:33 am
Forum: Vensim
Topic: new problem
Replies: 18
Views: 7797

Thanks very much for your help Bob. Could you please give me the equation for "planes waiting repair"? I entered an equation that I thought it should be, but got a simultaneous equation error.

Thanks again.

Nik
by nikvyas
Fri Nov 17, 2006 8:20 am
Forum: Vensim
Topic: new problem
Replies: 18
Views: 7797

Thanks again Bob..................however I don't think I have explained clearly enough! Before I explain, could I say that we will be having training courses in December and I will be able to ask Lee Jones to clarify a few of my weak points - however I need to demonstate to my leaders that Vensim i...
by nikvyas
Thu Nov 16, 2006 10:55 am
Forum: Vensim
Topic: new problem
Replies: 18
Views: 7797

Thanks for your comments Bob - I have to admit I'm a bit sloppy when it comes to that sort of thing. However, are you able to understand the problem I have re: the actual number of aircraft that are awaiting repairs? Unfortunately, the model is solely intended to show the actual aircraft awaiting re...