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st: RE: Assigning value to highest rank


From   "Tonya Cropper" <tonya_cropper@ksgphd.harvard.edu>
To   "Statalist" <statalist-digest@hsphsun2.harvard.edu>
Subject   st: RE: Assigning value to highest rank
Date   Mon, 24 May 2004 14:36:36 -0400

Thanks Nick.  This works great.  I didn't use the newvar2 since I really
need only the three outcomes to do further testing.

Tonya

      From   "Nick Cox" <n.j.cox@durham.ac.uk>
      To   <statalist@hsphsun2.harvard.edu>
      Subject   st: RE: Assigning value to highest rank
      Date   Mon, 24 May 2004 12:24:36 +0100

----------------------------------------------------------------------------
----

There may be a neater way than this rather
awkward grinding through cases:

First you can generate a row maximum by

gen max = max(pl,pd,pu)

Then the number of values equal to the maximum is

gen nmax = (pd == max) + (pu == max) + (pl == max)

The case of a unique maximum is

gen newvar = (pd == max) + 0.5 * (pu == max) if nmax == 1

Then your ties between two are

replace newvar = cond(uniform() < 0.5, 1, 0.5) if pd == max & pu == max
replace newvar = cond(uniform() < 0.5, 0.5, 0) if pu == max & pl == max
replace newvar = cond(uniform() < 0.5, 1, 0) if pd == max & pl == max

Presumably the case of three ties needs addressing

gen random = uniform()
replace newvar = cond(random < 1/3, 1, cond(random < 2/3, 0.5, 0)) if nmax
== 3

Any interest in

gen newvar2 = ((pd == max) + 0.5 * (pl == max))  / nmax

as a simpler scoring system? That way,

pd is unique max => 1
pl is unique max => 0.5
pu is unique max => 0
pd and pl tie    => 0.75
pd and pu tie    => 0.5
pl and pu tie    => 0.25
pd, pl, pu tie   => 0.5

Nick
n.j.cox@durham.ac.uk

Tonya Cropper
>
> I  have three variables within each observation that I am
> trying to assign a
> value for a new variable based on which of my three variables have the
> highest value.  If the highest value is pl,  I would like to
> assign newvar =
> 0, if the highest value is pd: newvar = 1, or if the highest
> value is pu:
> newvar = 0.5.  However, if there's a tie for the highest
> value, I would like
> to randomly choose the winner and then assign the value as above.
>
>
>
> Here's an example of the data and what I would want newvar to
> indicate.  I
> would greatly appreciate any assistance.  Thank you.
>
>
>
> Id         pd             pl            pu             newvar
>
> 117     11              11            8             (1 or 0
> based on whether
> pd or pl win toss)
>
> 118     12              8              10            1
>
> 120     18              10             14           1
>
> 121      6               11              7            0
>
> 122      4               9                9            (0 or
> 0.5 based on
> whether pl or pu win toss)
>
> 123      6               8                10          0.5
>
> 126      9               9                12          0.5
>
> 127      10             7                10          (1 or
> 0.5 based on
> whether pd or pu win toss)
>
> 129      9               11              10           0
>
> 131      9               5                 4            1
>
> 132      4                5                9            0.5


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