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st: RE: Check existence within a group
Nick, thank you very much. I was not familiar with this structure of
generating variables by assigning them a value and adding extra
conditions, like this:
_n > 1
I think I still need time to digest this as I don't understand very well
the structure behind this command. It has certainly been very useful,
though. Thank you.
And just a comment about the way I want to construct this dummy (I guess
you would code 1 for new and 0 for old), think of it as if the dummy
signaled when the borrower has already "experience" in a particular
market type. This construction is better for our own regression
> -----Original Message-----
> From: Nick Cox [mailto:firstname.lastname@example.org]
> Sent: Friday, May 07, 2004 10:54 AM
> To: email@example.com
> Subject: st: Check existence within a group
> Your guess is right. You don't need a loop at all.
> Stata is very good at doing this kind of thing
> without loops.
> Your variable -newmkttype- is coded 0 for new, 1 for old.
> Not the way that I would do it, but that's not important.
> You can get it from
> bysort borrower mkttype (issuedate) : gen newmkttype = _n > 1
> That is we sort first on -borrower-, within -borrower- on
> -mkttype-, and within -mkttype- on -issuedate-. Then you want
> the first occurrence within blocks of -borrower mkttype-
> to be flagged as new, by coding as 0, and later occurrences as
> not new, and so coded 1. This is achieved by
> _n > 1
> which evaluates as 0 if _n == 1 and 1 otherwise.
> de la Garza, Adrian
> > I have a database that contains info on bonds issued as follows:
> > borrower issuedate mtydate amount mkttype
> > ABN Amro 04Jun93 03Jun98 50 E
> > ABN Amro 19Sep94 17Jul96 100 E
> > ABN Amro 22Nov94 21Nov98 50 S
> > ...
> > ACINDAR 02Feb92 30Jan99 200 L
> > ACINDAR 20Mar92 19Mar97 50 E
> > ACINDAR 29Jul94 28Mar00 175 L
> > ...
> > and I want to create a variable -newmkttype- that tells me if the
> > borrower is issuing a bond in a completely new and unknown
> > market type.
> > If it is, then I want this variable to take the value of 0.
> If, on the
> > contrary, the borrower has issued bonds in this market type
> > in the past,
> > then I want this variable to take the value of 1 (notice that the
> > database is sorted by borrower issuedate mtydate amount).
> > borrower issuedate mtydate amount mkttype newmkttype
> > ABN Amro 04Jun93 03Jun98 50 E 0
> > ABN Amro 19Sep94 17Jul96 100 E 1
> > ABN Amro 22Nov94 21Nov98 50 S 0
> > ...
> > ACINDAR 02Feb92 30Jan99 200 L 0
> > ACINDAR 20Mar92 19Mar97 50 E 0
> > ACINDAR 29Jul94 28Mar00 175 L 1
> > ...
> > How can I construct this variable? Is there an easy way of
> > checking the
> > borrower's history to determine whether -newmkttype- should
> > get a 0 or a
> > 1, without writing a complicated loop?
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