[Jprogramming] Verb for computing a changeable expression

[David Vaughan]

Either I am misunderstanding or that is not correct.

For 4 turns, the probability is 11r120. It doesn't look like that verb will produce that - actually trying the whole verb gives me a domain error as well.

On 19 Oct 2011, at 17:03, Marshall Lochbaum wrote:

> The number of ways to choose k red balls is the sum over all combinations of
> bags of the probability you draw a red ball from each of those bags,
> multiplied by the number of ways to choose the red balls, which is 1. So, I
> suggest you find one of the various comb verbs running around, and then
> something like
> (+/ */"1 k comb n) % (!>:n)
> will give you that probability. Then make this into a verb dependent on k,
> apply it with rank zero to (i.<.-:<:n), and add those results up.
> 
> Marshall
> 
> On Wed, Oct 19, 2011 at 11:09 AM, David Vaughan <
> purpleblues13 at googlemail.com> wrote:
> 
>> That was untested - hence errors.
>> 
>> If r and b are two choices, and you start with a bag containing r,b and
>> after each turn where you take one item from the bag you add another r. The
>> goal is to find the probability of choosing more b's than r's. As I probably
>> haven't explained well, here's an example:
>> 
>> b,r - take b, return it and add another r
>> b,r,r - take r, return it and add another r
>> b,r,r,r - take b, return it.
>> 
>> In this case there were 3 turns, and 2 b's were chosen vs 1 r, so that is a
>> success. The probability of taking more b's than r's is the probability of
>> taking 3 b's = %24 plus the probability of taking 2 b's and 1 r = 24%~1+2+3
>> which gives 7r24. Though I'm not actually sure my idea for the general case
>> is totally correct.
>> 
>> On 19 Oct 2011, at 15:48, Marshall Lochbaum wrote:
>> 
>>> The correct way is to compute all the terms in the expression and then
>>> multiply them together. Something like
>>>  n* > *&.>/ >:@i.&.> n->:i.k
>>> However, the expressions you gave will return length errors, since
>> (>:i.n-2)
>>> is patently not the same length as (>:i.n-1). What exactly are you trying
>> to
>>> compute?
>>> 
>>> Marshall
>>> 
>>> On Wed, Oct 19, 2011 at 10:39 AM, David Vaughan <
>>> purpleblues13 at googlemail.com> wrote:
>>> 
>>>> I couldn't really think of an appropriate title for this. My issue is
>> that
>>>> I want to compute an expression that has a different number of terms
>>>> depending on y.
>>>> 
>>>> +/(>:i.n-1)*n NB. for all n, y >: n > 1
>>>> +/(>:i.n-2)*(>:i.n-1)*n NB. for all n, y >: n > 2
>>>> 
>>>> and so on, so that:
>>>> 
>>>> lim =. <:<.y%2
>>>> 
>>>> and we carry on the style of expression above until we are doing it for
>> all
>>>> n, y >: n > lim.
>>>> 
>>>> So in the case for y=.5, lim=.1 and we only do the first of the lines
>>>> above. For y=.7, we would do the second one as well. For y=.9 we would
>> do
>>>> the same as the second but with a (>:i.n-3) multiplied with it all as
>> well.
>>>> I guess/hope there is some way of achieving this with power?
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