reports and prices [Patch] reworked advanced-portfolio.scm

[Christian Stimming]

Hi Andrew and Mark,

Am Samstag, 18. Februar 2006 18:20 schrieb Mark Johnson:
> >2) you can always come in the next day and record the current price for
> > the fund so that the pricedb shows the current value. Make sense? the
> > only thing you'll lose will be the price history. Its okay that you don't
> > show the current market price at the time of the transfer/exchange. you
> > can always provide that number later so that your reports show the
> > current market value.
>
> True.  What about the possibility of reports based upon the pricedb
> entries?  Eg. a graph of the price history.  Such entries would produce
> unwelcome blips.  I'm just thinking here about possible future features,
> and, I suppose, the meaning of pricedb entries.

Just to remind you of the current reports and so that everyone is on the same 
page: The distinction between prices "from the pricedb" and those calculated 
"implictly from existing transactions" has always existed and had to be dealt 
with always. 

The report that shows the development of a price over time (the "Price 
Scatterplot"), as well as all the other reports that depend on exchange 
prices, has therefore the option of choosing the "price source". I 
implemented that at the time because to me the only meaningful choices here 
were 1. either prices from the pricedb, *or* 2. implicit prices, but no mix 
of both. That's why the option "price source" has one choice to use the 
"implicit prices" and two other choices that will use prices "from the 
pricedb". So the solution to this two choices has been to give the user the 
option to choose between one out of two methods. I'm actually quite sure that 
any mix between both methods, at least for the same commodity, really doesn't 
give meaningful results. The "exchange-fn" IIRC should be the abstraction to 
provide access to both methods the same way. The way the exchange-fn was 
calculated is probably not the most efficient one, but at least it gave 
accurate results for the choices that were available. 

However, although I coded quite a lot of the multi-currency stuff, this is all 
now quite a long time ago and I don't remember anything I ever did at the 
time. Hopefully I added enough comments in the scheme code.

In summary: The question of the price source has been an issue since the 
introduction of the pricedb to gnucash, and it had to be solved in all 
multi-commodity reports, not only the advanced-portfolio.scm. If you think 
the available reportsystem-wide implementation needs changes, you are of 
course welcome to do them, but please keep in mind that this whole issue is 
really not trivial. In particular, both price source options are pretty much 
orthogonal to each other and I haven't heard any convincing proposal to mix 
them, so I'd rather suggest to continue to treat both separately at some 
level.

Regards,

Christian