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From |
Nick Cox <njcoxstata@gmail.com> |

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

Subject |
Re: st: Problem with local macro command and marginsplot |

Date |
Fri, 7 Jun 2013 09:36:38 +0100 |

I see no evidence here that implies a bug. It's much more likely that there is a problem with your understanding of local macros. First off, there is a big difference between local m_x r(p50) which assigns the text "r(p50)" to the local macro, regardless of (1) whether r(p50) currently is defined (2) what its current value may be and local m_y = r(p50) which assigns the current numeric value of r(p50) (which might be missing). Stata will never complain that r(p50) is undefined; invoking r(p50) is never a syntax or logic error, but if the result is missing, commands downstream may produce puzzling results. Second, if local macro -foo- is defined di ` foo ' with extra spaces won't -display- it. You must type `foo'. A quick way to check what is defined among local macros -- in addition to -display- -- is the command -mac li-. I don't understand your question about -margins-. The report "it works but I got an error" needs to be fleshed out with complete and exact detail. Nick njcoxstata@gmail.com On 7 June 2013 08:38, Baruffaldi Stefano Horst <stefano.baruffaldi@epfl.ch> wrote: > I have a problem with the local macro command. I really tried everything and I cannot find any logic for this problem – unless it is a bug. > I could find no previous post that addressed a similar issue. > > I am running the following command: > > sum x, d > local m_x r(p50) > local low_x r(p25) > local high_x r(p75) > > sum y, d > local m_y = r(p50) > local high_y = r(p25) > local low_y = r(p75) > > qui: xtreg vardep c.y ##c.x, fe > margins, at(x=(0(0.5)12) prior_diffy=( `low_y' `m_y' `high_y')) post > marginsplot, xlabel(0(0.5)12) xline(` low_x ' ` m_x ' ` high_x ') > > right after the margins command I get the error message: “invalid numlist” or “invalid numlist has too few elements”. > > After a while I figured out that probably the problem is the local command: if I type for instance [dis `m_y'] it shows that there is no value stored. But the most weird thing is that if I run [dis `m_y'] right after the sum command sometimes there is the value (sometimes not, especially if I run the command directly from the do-file). In any case, after I run the margins command (whether with post option or not) the “locals” are always empty. Furthermore I used a similar code in the past without problems. > > This is my main problem. > Additionally, I was wondering if there is a way to indicate directly in the margins command the percentiles of the variable I want to be considered. > I tried with: > > margins, at( (p25) y x=(0(0.5)12)) /// > at( (p50) y x=(0(0.5)12)) /// > at( (p75) y x=(0(0.5)12)) > > it works but I got an error after the marginsplot command saying that something more was expected > * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

**References**:**st: Problem with local macro command and marginsplot***From:*Baruffaldi Stefano Horst <stefano.baruffaldi@epfl.ch>

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