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
[email protected]
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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