Ben
> Perhaps you can specify your question more precisely, or differently.
> The way I interpret it, if there are no interactions in price
> (e.g. you get a discount for buying more than one book at a time)
> or in value (e.g. you learn more from one book having read another),
> then you get the best value/price ratio by taking only the book with
> the highest value/price. (If you take no books at all, your value/price
> ratio is undefined.) The algebra below shows that combining a lower
> value/price book with a higher one always lowers your overall value/price
> ratio.
>
Thanks, for the pointers on R functions. My question was as superficial as
it sounded. I have a commercial programme that does this (one of several
that are available), and wondered if there was an R package that provided
the same tools. It's a common tool, and I had hoped to have explained enough
to allow an appropriate package to be identified, so I could have a quick
look at what it does.
But having started this, I now feel obliged to clarify the question. I only
chose books as an easy example, you could substitute alternative marketing
strategies, monitoring programmes, choice of ornaments for a new house, or
holidays etc. So there could be only a few potential combinations or
hundreds.
But to stick with the books, and only three options: A, B and C
Book A costs $100 and I have given it a subjective value of 50
Book B costs $36 and I have given it a subjective value of 60
Book C costs $50 and I have given it a subjective value of 80
So book A is costing me $2 per value unit, Book B $0.6 per value unit and
book C £0.63 per value unit.
Buying books A+B gives me a $1.24 per value unit
Buying books A+C gives $1.07 per value unit
Buying books B+C gives 0.61 per value unit
Buying books A+B+C gives 0.97 per value unit
So in terms of value for money, there are three contenders
Book B on its own, Book C on its own, or buying both books B and C.
Book B $36.00 and value 60
Book C $50.00 and value 80
Book B+C at $76.00 and value 140
Depending on how you are using this tool, you can either use it to decide
how spend an existing budget, or use it to set a budget.
Seems hardly worth the bother for three books but if you are looking at 20
books or 30 different monitoring options etc, it gives a useful insight into
how best to spend or set a budget
The commercial software graphs this costs vs values so you usually end up
with some sort of an asymptotic graph where you can see that spending below
a certain budget gives a very poor return.
Graham
[[alternative HTML version deleted]]
______________________________________________
R-help@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
