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I just learned that I can create a Dataset by combining Dataset and Table functions. For example:

d = RandomVariate[DemandProcess, nperiods];
dat = Table[<|
  "d" -> d[[i]],
  "underQ" -> Boole[d[[i]] > Q] (d[[i]] - Q),
  "overQ" -> Boole[d[[i]] <= Q] (-d[[i]] + Q),
  "under$" -> Boole[d[[i]] > Q] (d[[i]] - Q) cu,
  "over$" -> Boole[d[[i]] <= Q] (-d[[i]] + Q) co,
  "iQ" -> If[i == 1, Q, 0]
  |>, {i, 1, nperiods}];
dat = Dataset[dat]

result of dataset on table

For anyone interested in the background of this problem, this is a newsvendor model where Q is quantity of inventory to order in every period, d is a list of demand quantities per period, underQ is shortage of inventory, under\$ is cost of the shortage, cu is the cost of unit shortage; overQ, over\$, co have similar meanings; rows are periods and inventory doesn't carry over.

Now, where I'm struggling is the iQ column: I want its consecutive values to depend on preceding values. I could achieve that, for example, by doing this:

RecurrenceTable[{iQ[t + 1] == 
  iQ[t] + Boole[iQ[t] < d[[t]]] cu - Boole[iQ[t] > d[[t]]] co, 
  iQ[1] == iQstart}, iQ, {t, 1, nperiods}]

I don't think that this is achievable by using Table function and I don't know how to combine Dataset function with the above RecurrenceTable code.

Please help and advise on how to keep the solution compact and neat. Thank you

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  • $\begingroup$ For such a simple recurrence you gave you can directly do the same with Table so you can write "iQ"->(q=q+1) where of course q=Q is set before the table starts. But for more complicated recurrence you'll probably have to run the recurrence table first q=RecurrenceTable[...] then only create the dataset the same way you did but "iQ"->q[[i]]. $\endgroup$
    – SquareOne
    Commented Sep 30, 2017 at 9:12
  • $\begingroup$ Thanks @SquareOne but my RecurrenceTable code shows a code that I made up to save me some typing, not the actual code. I should have realized that. I'll edit my question with the actual code. $\endgroup$
    – Houston Mooncat
    Commented Sep 30, 2017 at 12:28
  • $\begingroup$ Your actual code for the RecurrenceTable can be easily translated to Table. Run this for example:q=iQstart ; Table[q=q+Boole[q<d[[t]]] cu - Boole[q>d[[t]]] co, {t,1,nperiods}]. Then, you can directly use it inside your dat command to build the dataset. $\endgroup$
    – SquareOne
    Commented Sep 30, 2017 at 20:47

1 Answer 1

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Just happened across this. If I understand the situation, you're looking for an accumulation of iQ (over time) as you proceed down the dataset. I do loads of this type of thing with time series. I've simplified from your example, hope this helps:

dat[Query[<|
  "d" -> Query[All, "d"],
  "d(rand)" -> Query[All, "d(rand)"], 
  "d(accum)" -> Query[Accumulate, "d(rand)"]
|>]]
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  • $\begingroup$ Please show that this addresses the question by including the result of your code. $\endgroup$
    – bbgodfrey
    Commented Feb 8, 2018 at 19:54

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