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

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

Subject |
Re: st: Need help with Stata Programming |

Date |
Thu, 30 May 2013 20:20:16 +0100 |

Let me expand for the sake of anyone interested in that but finding it too obscure. The context is one in which we are looping any way. It doesn' t matter how we are looping. Here we happen to be looping over filenames and the whole pattern is just this cycle foreach <filename> { read data do stuff write results } (come to think of it, that's most of statistics, but never mind) PLUS the details. So, what Michael wants is also to loop simultaneously over years 2000, ... and it is easy to add that too. There is an initialisation before the loop, say to local y = 1999 Then inside the loop we could go local y = `y' + 1 except that Stata has a shorthand for that local ++y which is stolen from the C programming language (which in turn ...) as a special notation for adding 1, or bumping up as many programmers like to say. (At this point, a very delicate detail is that Stata does not allow local y++ as an alternative way of adding 1. That is legal but what it does is assign the string "++" to the macro name -y-. The explanation in turn is that it's wired into Stata that whatever follows a legal macro name is its new contents (no need for a space either). Too late to change that. Digression within digression: If you know that in C there is subtle and important difference between ++ as prefix and ++ as suffix, that's correct, but it is not going to be part of this story.) That's it. Note that this extra looping is not specified by complicating the -foreach- loop. It's just something we can do for ourselves, given that Stata is looping anyway. Nick njcoxstata@gmail.com On 30 May 2013 19:58, Nick Cox <njcoxstata@gmail.com> wrote: > Nick > njcoxstata@gmail.com > > local ds1 "D:\_Dummy\multiple\1\auto_1.dta" > local ds2 "D:\_Dummy\multiple\2\auto_2.dta" > local ds3 "D:\_Dummy\multiple\3\auto_3.dta" > local all ds1 ds2 ds3 > local y = 1999 > foreach x in `all'{ > use ``x'',clear > include "D:\_Dummy\multiple\4\mpg.do" > include "D:\_Dummy\multiple\5\sum.do" > local ++y > gen year = "`y' " > save ``x''_new.dta,replace > } > > local ++y > > could be > > local y = `y' + 1 > > The whole thing could be shorter. > >> ************************************************ >> NOW MY NEW TASK/PROBLEM: >> I want to create a string variable "year" which needs to be 2000 for >> auto_1.dta, 2001 for auto_2.dta,2002 for auto_3.dta etc >> Is could open each dataset and create it myself before starting a the loop. >> But is there a way to create one OR more variables with different >> values for different datasets?? within a loop * * 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: Need help with Stata Programming***From:*Michael Stewart <michaelstewartresearch@gmail.com>

**Re: st: Need help with Stata Programming***From:*Nick Cox <njcoxstata@gmail.com>

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