}.({:@[ (] , *) +&{. + {:@])/\.&.|. 0 , A
1000 50
1050 42
1092 65.52
1657.52 82.876
1740.396 87.0198
R.E. Boss
> -----Oorspronkelijk bericht-----
> Van: [email protected] [mailto:programming-
> [email protected]] Namens Bill Harris
> Verzonden: zaterdag 18 juli 2009 4:49
> Aan: J Programming Forum
> Onderwerp: [Jprogramming] Accumulation, interest, and simulation
>
> I've got a problem to solve, and I seem to have a mental block, even
> though it doesn't sound that hard.
>
> Let's say I have an array A of rank n 2. To make it real, let {."1 A be
> a list of deposits to a savings account, and let {:"1 A be the periodic
> interest rate paid during that period. To simplify more, let's say each
> item represents a year's (or at least a constant period's) entry.
>
> For example, let A be
>
> 1000.0 0.05
> 0.0 0.04
> 0.0 0.06
> 500.0 0.05
> 0.0 0.05
>
> I'd like to calculate the interest earned as a function of time with a
> tacit function.
>
> There are many analogous problems; if I can solve this, I might even be
> able to do a system dynamics simulation in J. (I seem to remember an
> article in a 1990s J proceedings on doing system dynamics in J, but I
> haven't been able to find those proceedings in quite a while.)
>
> I can make an auxiliary array (or stitch more columns onto A) to contain
> both the current balance (the sum of the previous balance, the interest
> paid from the last period, and any new deposit) and the interest being
> earned in this period (the product of {:"1 A and the current balance).
>
> For example, let Aprime be
>
> 1000.00 0.05 1000.00 50.00
> 0.00 0.04 1050.00 42.00
> 0.00 0.06 1092.00 65.52
> 500.00 0.05 1157.52 57.88
> 0.00 0.05 1215.40 60.77
>
> I thought the linear recurrence essay might give me a hint, but it
> depends upon the transformation matrix M being a constant, and this one
> has a variable interest rate times a varying balance.
>
> Ideas?
>
> Thanks,
>
> Bill
> --
> Bill Harris http://facilitatedsystems.com/weblog/
> Facilitated Systems Everett, WA 98208 USA
> http://facilitatedsystems.com/ phone: +1 425 374-1845
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