Bookmark and Share

Notice: On April 23, 2014, Statalist moved from an email list to a forum, based at statalist.org.


[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: st: Doing something an observation-specific number of times


From   Austin Nichols <[email protected]>
To   [email protected]
Subject   Re: st: Doing something an observation-specific number of times
Date   Tue, 28 Aug 2012 13:23:11 -0400

robert hartman <[email protected]>:
If you google "sum of finite geometric series" or somesuch, you should
find an easy answer.

On Tue, Aug 28, 2012 at 12:45 PM, robert hartman <[email protected]> wrote:
> Hi Listers,
> Imagine that observation 1 has v1 and v2 values of .41 and 78,
> respectively. There are many other observations like this, where v1
> values lie on the unit interval and v2 values are positive integers
> (let's say the upper bounded is 600). I want to create a new variable
> and store in it the results of an algebraic equation that uses the v1
> and v2 values from same row, as well as some constants, and where
> "observation-specific exponentiation" is happening. For example, let's
> say I want to add a constant to v1 raised to some power and then
> divide that by some other constant. And let's say that the "some
> power" is  every power from 1 to the v2 value inclusive (e.g., 1
> through 78 in this case, 1 through 2 if the v2 value is 2...) and then
> sum up those terms.  For example, for observation 1, the new obs 1 v3
> value=((1+(.41^1))/2) + ((1+(.41^2))/2) ...((1+(.41^77))/2) +
> ((1+(.41^78))/2). The specific use case is convoluted, and I don't
> think in-depth understanding of it is critical to the programming
> (we'll see).
>
> I have begun to think of some klugy ways of doing this via looping or
> even the expand command. However, whereas my Stata programming skills
> are mediocre and have been acquired ad hoc, I thought some of you
> might have some insights as to a relatively computationally efficient
> and/or lines-of-code efficient way of doing this kind of thing. There
> may even be some kind of obvious (to you, not me) algebraic workaround
> that I'm not catching.
>
> Thanks,
> Rob
*
*   For searches and help try:
*   http://www.stata.com/help.cgi?search
*   http://www.stata.com/support/statalist/faq
*   http://www.ats.ucla.edu/stat/stata/


© Copyright 1996–2018 StataCorp LLC   |   Terms of use   |   Privacy   |   Contact us   |   Site index