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From |
"Nick Cox" <n.j.cox@durham.ac.uk> |

To |
<statalist@hsphsun2.harvard.edu> |

Subject |
st: RE: Problem with "while" and "for" loops. |

Date |
Mon, 24 Jun 2002 13:19:05 +0100 |

Sanmitra Ghosh wrote > I am trying to calculate trend corrected coefficient > of variation. But the do file is not running properly. > I tried it using both while and for loops. The problem > with the while loop is that if there is any missing > value for the group variable, the do file terminates > there giving a r(2000) message. This problem doesn't > occur with the for loop, since there is a nostop > option. However, it is giving another error message > which is r(123), i.e. numlist has too many numbers. I > don't know how to get rid of these problems. Could > anyone kindly give me some suggestions? I am attaching > the do files. First, please note that Statalist members are asked _not_ to send attachments to the list, for the usual reasons (members whose software cannot handle attachments, precautions against viruses, etc.). This is explained in the FAQ. Sanmitra's -trial1.do- was use "C:\WINDOWS\DESKTOP\temp.dta" sort stcode distcode time sum stdist local min = r(min) local max = r(max) gen trend1 = 0 local i = 1980 while `i' <= 1991 { local j = `i' - 1979 replace trend1 = `j' if time == `i' local i = `i' + 1} gen trend2 = 0 local i = 1992 while `i' <= 2000 { local j = `i' - 1991 replace trend2 = `j' if time == `i' local i = `i' + 1} gen period = 0 replace period = 1 if time >= 1992 gen adjrsq1 = 0 gen adjrsq2 = 0 local x = `min' while `x' <= `max'{ reg crop trend1 if (stdist == `x' & period == 0) replace adjrsq1 = e(r2_a) if (stdist == `x' & period == 0) reg crop trend2 if (stdist == `x' & period == 1) replace adjrsq2 = e(r2_a) if (stdist == `x' & period == 1) local x = `x' + 1} macro drop _min _max _i _j _x gen cov1 = sqrt(covarr1*(1 - adjrsq1*adjrsq1)) gen cov2 = sqrt(covarr2*(1 - adjrsq2*adjrsq2)) and -trial2.do- was use "C:\WINDOWS\DESKTOP\temp.dta" sort stcode distcode time sum stdist local min = r(min) local max = r(max) gen trend1 = 0 local i = 1980 while `i' <= 1991 { local j = `i' - 1979 replace trend1 = `j' if time == `i' local i = `i' + 1} gen trend2 = 0 local i = 1992 while `i' <= 2000 { local j = `i' - 1991 replace trend2 = `j' if time == `i' local i = `i' + 1} gen period = 0 replace period = 1 if time >= 1992 gen adjrsq1 = 0 gen adjrsq2 = 0 for NUM in num `min'/`max', nos : reg crop trend1 if (stdist == NUM & period == 0) \replace adjrsq1 = e(r2_a) if (stdist == NUM & period == 0) \reg crop trend2 if (stdist == NUM & period == 1) \replace adjrsq2 = e(r2_a) if (stdist == NUM & period == 1) macro drop _min _max _i _j gen cov1 = sqrt(covarr1*(1 - adjrsq1*adjrsq1)) gen cov2 = sqrt(covarr2*(1 - adjrsq2*adjrsq2)) One approach to the troublesome loop is to learn about -capture-. local x = `min' while `x' <= `max'{ reg crop trend1 if (stdist == `x' & period == 0) replace adjrsq1 = e(r2_a) if (stdist == `x' & period == 0) reg crop trend2 if (stdist == `x' & period == 1) replace adjrsq2 = e(r2_a) if (stdist == `x' & period == 1) local x = `x' + 1 } I guess that the problem arises if -stdist- is never equal to a particular value of `x'. In that circumstance the regression will crash, and the -replace- statement following must not be attempted: local x = `min' while `x' <= `max'{ capture reg crop trend1 if (stdist == `x' & period == 0) if _rc == 0 { replace adjrsq1 = e(r2_a) if (stdist == `x' & period == 0) } capture reg crop trend2 if (stdist == `x' & period == 1) if _rc == 0 { replace adjrsq2 = e(r2_a) if (stdist == `x' & period == 1) } local x = `x' + 1 } A secondary point is that in Stata 7, -forvalues- is nicer for this construct: forval x = `min'/`max'{ capture reg crop trend1 if (stdist == `x' & period == 0) if _rc == 0 { replace adjrsq1 = e(r2_a) if (stdist == `x' & period == 0) } capture reg crop trend2 if (stdist == `x' & period == 1) if _rc == 0 { replace adjrsq2 = e(r2_a) if (stdist == `x' & period == 1) } } Another secondary point is that -if e(sample)- is useful, here and elsewhere, if only as a matter of conciseness: forval x = `min'/`max'{ capture reg crop trend1 if (stdist == `x' & period == 0) if _rc == 0 { replace adjrsq1 = e(r2_a) if e(sample) } capture reg crop trend2 if (stdist == `x' & period == 1) if _rc == 0 { replace adjrsq2 = e(r2_a) if e(sample) } } I can't identify what is wrong with the numlist. An FAQ in this territory -- cycling through all possible values -- http://www.stata.com/support/faqs/data/for.html Nick n.j.cox@durham.ac.uk * * For searches and help try: * http://www.stata.com/support/faqs/res/findit.html * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: RE: Problem with "while" and "for" loops.***From:*Sanmitra Ghosh <sanmitraz@yahoo.co.uk>

**References**:**st: Problem with "while" and "for" loops.***From:*Sanmitra Ghosh <sanmitraz@yahoo.co.uk>

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