dear forum,
i intend to calculate investment model (to find out investment period and NPV) and I made a submodel like the attached one. But surprisingly the result was different from manual calculation using Excel.
Can anybody help telling me what went wrong with my model?
Thanks and regards
different result
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Re: different result
It's impossible to help with just screen shots.
Have you reviewed the documentation for the NPV/NPVE functions?
http://www.vensim.com/documentation/fn_npv.html
http://www.vensim.com/documentation/fn_npve.html
Have you reviewed the documentation for the NPV/NPVE functions?
http://www.vensim.com/documentation/fn_npv.html
http://www.vensim.com/documentation/fn_npve.html
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
Re: different result
sorry I forgot to attach the model
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- Super Administrator
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Re: different result
Still not possible to help you. You haven't provided the spreadsheet so we can see the calculations or instructions on what to look at.
I'd suggest making sure the model passes the units check before you start comparing it with other calculations.
My guess is that the equation for "harga sewa" is incorrect. You are accumulating the rate plus the level itself. This is similar to
x(t) = x(t-1) + x(t-1) + rate
I'd suggest making sure the model passes the units check before you start comparing it with other calculations.
My guess is that the equation for "harga sewa" is incorrect. You are accumulating the rate plus the level itself. This is similar to
x(t) = x(t-1) + x(t-1) + rate
Advice to posters seeking help (it really helps us to help you)
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
http://www.ventanasystems.co.uk/forum/v ... f=2&t=4391
Units are important!
http://www.bbc.co.uk/news/magazine-27509559
Re: different result
I think the key problem here is indeed the equation for harga sewa. Currently it is:
INTEG( rate harga sewa+harga sewa, 25000)
but it probably should be
INTEG( rate harga sewa, 25000)
Units checking would reveal the error, if units were defined.
INTEG( rate harga sewa+harga sewa, 25000)
but it probably should be
INTEG( rate harga sewa, 25000)
Units checking would reveal the error, if units were defined.
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