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Re: st: Matrix zeros and ones

From   Maarten Buis <[email protected]>
To   [email protected]
Subject   Re: st: Matrix zeros and ones
Date   Mon, 22 Aug 2011 14:20:34 +0200

On Mon, Aug 22, 2011 at 1:59 PM, Tribin Uribe, Ana wrote:
> I have  data  about  letters that have been sign by a group of people
> Letter   signatures
> Letter1 Friend1
> Letter2 Friend2 Friend3 Friend4 Friend5
> Letter3 Friend4
> I want to create with this information  a matrix with zeros and ones,
> like this one using information above
> Letter Friend1  Friend2  Friend3 Friend4 Friend5
> Letter1 1 0 0 0 0
> Letter2  0 1 1 1 1
> Letter3  0 0 0 1 0

*----------------------- begin example ---------------------
input ///
Letter  str31 signatures
1             "Friend1"
2             "Friend2 Friend3 Friend4 Friend5"
3             "Friend4"

gen byte friend1 = strpos(signatures, "Friend1") > 0
gen byte friend2 = strpos(signatures, "Friend2") > 0
gen byte friend3 = strpos(signatures, "Friend3") > 0
gen byte friend4 = strpos(signatures, "Friend4") > 0
gen byte friend5 = strpos(signatures, "Friend5") > 0

l Letter friend*
*--------------------- end example ------------------------
(For more on examples I sent to the Statalist see: )

There are however two things I would worry about: 1) Your data is
stored as a string variable, and these can only contain 244 characters
(including spaces). I can easily imagine letters signed by groups of
people where that limit is surpassed. 2) When signing people can
easily use other variations of their own name (Maarten, Maarten Buis,
M. Buis, dr. M. Buis, Dr. M. Buis, dr. M.L. Buis, dr. M. L. Buis
(extra space between M. and L.), Maarten Leendert Buis, Maarten L.
Buis, etc. etc.). Even if people are consistent in the way they sign
their name, the person that typed them in could easily make typos (an
incomplete list of variations on my name that have appeared on this
list is: Marteen, Maarteen, Maarrten, Martin). The strategy used above
is very sensitive to such variations.

Hope this helps,

Maarten L. Buis
Institut fuer Soziologie
Universitaet Tuebingen
Wilhelmstrasse 36
72074 Tuebingen
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