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st: RE: RE: Bracket [ ] notation


From   "Terra Curtis" <terra.curtis@cambridgefinance.com>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: RE: Bracket [ ] notation
Date   Wed, 10 Aug 2005 10:28:22 -0400

Is there any way to tell Stata to ignore the command when at least one of
the referenced entries does not exist?
 

-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nick Cox
Sent: Tuesday, August 09, 2005 5:09 PM
To: statalist@hsphsun2.harvard.edu
Subject: st: RE: Bracket [ ] notation

If the subscript on the RHS is missing (meaning not present in the dataset),
the result on the LHS will be missing too (meaning "missing"). 

Here the use of -by:- is just a detail and does not affect the principle.
The principle can be seen by 

sysuse auto
di mpg[0]
di mpg[75] 

As advised in another thread, you would surely be better off re-casting this
using time-series operators. 

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

P.S. the spelling is Stata. 

Terra Curtis
 
> I am running into some problems trying to run a nonlinear regression.  
> I continue to get error 480 "starting values invalid or some RHS 
> variables have missing values."  I think I see where my error is but 
> I'm not sure how STATA deals with a reference, say 'by varname: 
> data[x]' if x is out of the range of data for that varname.  Here is 
> my code:  I have written a program to specify the nonlinear equation, 
> and that is where the error is:
> 
> program nlstk2_depreciation
> 	version 8.1
> 	if "`1'" == "?" {
> 		global S_1 "B3 B4 B5 drd2 dmktg2"
> 		global B3=1
> 		global B4=1
> 		global B5=1
> 		global drd2=0.15
> 		global dmktg2=0.15
> 		exit
> 	}
> 	forvalues x=10/53 {
> 		by coname: replace `1'=$B3+$B4*(ireal46[`x'] + 
> (1-$drd2)*ireal46[`x'-1] + (1-$drd2)^2*ireal46[`x'-2] + 
> (1-$drd2)^3*ireal46[`x'-3] + (1-$drd2)^4*ireal46[`x'-4] + 
> (1-$drd2)^5*ireal46[`x'-5] + (1-$drd2)^6*ireal46[`x'-6] + 
> (1-$drd2)^7*ireal46[`x'-7]+ (1-$drd2)^8*ireal46[`x'-8] +
> (1-$drd2)^9*ireal46[`x'-9]/$drd2) + $B5*(imktg[`x'] + 
> (1-$dmktg2)*imktg[`x'-1] + (1-$dmktg2)^2*imktg[`x'-2] + 
> (1-$dmktg2)^3*imktg[`x'-3] + (1-$dmktg2)^4*imktg[`x'-4] + 
> (1-$dmktg2)^5*imktg[`x'-5] + (1-$dmktg2)^6*imktg[`x'-6] + 
> (1-$dmktg2)^7*imktg[`x'-7] + (1-$dmktg2)^8*imktg[`x'-8] +
> (1-$dmktg2)^9*imktg[`x'-9]/$dmktg2) if `x'==year
> 	}
> end
> 
> I have panel data for companies over a period of years, although each 
> company has a different amount of years of data (no company has more 
> than 53 years of data).  If a company has 10 years of data, I want the 
> regression to use all 10 years of data.  If it has more than 10 years 
> of data, I want it to use the most recent 10 (say, years 1990-1999), 
> then use the next 10 (years 1989-1998), and so on until it gets to the 
> last set of 10 years for that company.  I think the logic of the 
> equation I have written works out, so I'm guessing the error is coming 
> from some referencing problem in the brackets...I don't quite 
> understand how STATA would deal with ireal46[49] if some company 
> didn't have a 49th ireal46 entry.
> 

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