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

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

Subject |
RE: st: Selecting stubnames for -reshape- / macrolists |

Date |
Mon, 30 Jun 2008 17:37:34 +0100 |

This problem is discussed in an FAQ: FAQ . . . . . . . . . . . . . . . . . . . . . . . . Problems with reshape 12/03 I am having problems with the reshape command. Can you give further guidance? http://www.stata.com/support/faqs/data/reshape3.html However, what is there does not add much to your discussion. ================= extract from FAQ Question If I have many variables all occurring in pairs for two years 1997 and 1998, so that the dataset looks like A97, A98, B97, B98, and so on, is there any easy way to reshape the data to long without typing all the stub names? Answer The variable names are collectively *97 *98, so we need a way of expanding that list of wildcard names automatically and then removing the suffix. We can work on either *97 or *98. -unab- is usually billed as a programmer's command, but it can be used interactively. It unabbreviates a varlist and puts the result in a local macro. . unab vars : *97 Then we zap all the occurrences of the suffix "97": . local stubs : subinstr local vars "97" "", all In other words, each occurrence of "97" is replaced by an empty string; that is, they are removed. See help on -macro-. Then we can . reshape long `stubs', options ================================ That said, it is possible to write a program more general than Paul's. *! NJC 1.0.0 30 June 2008 * collects stubs of form prefix_ from varlist * with names of form prefix_suffix * call by e.g. stubs *_* program stubs version 8.2 syntax varlist foreach v of local varlist { local stub = substr("`v'", 1, strpos("`v'", "_")) if !`: list stub in all' { local all `all' `stub' } } c_local stubs `all' end If you run . stubs *_* on your example dataset, you'll find a local stubs containing x_ y_ left behind. Nick n.j.cox@durham.ac.uk Philipp Rehm . Thanks, Paul. You wrote: "You will want to make sure that if your subscripts all look like _1, _2, _3... that you only use one of them. Grabbing *_* will give the same stubname many times." Alas, that's exactly my problem. I need to grab *_*, because I don't know which subscripts are present or absent. (Since this may sound a little strange, let me explain why this is so. I have a data-set with thousands of variables over a maximum of 40 years or so, in wide format. The problem is that not all variables are present for all years, which is why I prefer to grab everything and get the stubs from there). E. Paul Wileyto wrote: > I have the following implemented as an ADO. It is what I use to grab > all the name stubs for reshaping. You will want to make sure that if > your subscripts all look like _1, _2, _3... that you only use one of > them. Grabbing *_* will give the same stubname many times. > > Paul > > program define namelist > > *********************************************************************** > *********************************************************************** > * This short program helps you define a list (global macro vlist) > * of variable name roots to aid in scripting and especially reshaping. > * > * Feel free to use wildcards in varlist. Be sure that you are only > * generating the same root once. > * > * The oldsub option describes the common subscript in the the list. > * The newsub option describes the truncated subscript to be used in > * reshaping. > * * For example: Variables rx30a_s1..rx30a_s20 all have the common root > * rx30a_s, with a numerical subscript for the repetition. To extract a > * list of roots for all survey entries, use: > * > * -namelist rx*_s1, oldsub(_s1) newsub(_s) > * > *********************************************************************** > *********************************************************************** > > syntax varlist, [oldsub(string) newsub(string)] > global vlist "`varlist'" > if "`oldsub'" > "" & "`newsub'" > "" { > global vlist : subinstr local varlist "`oldsub'" "`newsub'" , all > } > noisily ma list vlist > end > > > pr9@duke.edu wrote: >> . >> My question is whether there is a clever way to identify the stubnames >> for a -reshape-. Consider this example: >> >> sysuse auto, clear >> foreach j in 1 2 3 4 5 { >> gen x_`j'=rep78+`j' >> gen y_`j'=rep78-`j' >> } >> drop y_3 >> gen id=_n >> keep id x_* y_* >> >> /* >> This data-set contains the following variables which I want to -reshape-: >> x_1 x_2 x_3 x_4 x_5 >> y_1 y_2 y_4 y_5 >> I want to -reshape- by stubnames x_ and y_. >> In my "real" data-set, I know that all variables I want to end up with >> as stubnames contain an underscore (_). They all also do contain numbers >> after the underscore, but there is no regular pattern there. >> >> Now, I am generating a -macrolist- with unique stubnames, but this seems >> like a detour to me, especially the loop: >> */ >> >> ds *_* >> foreach v in `r(varlist)' { >> local f `=regexr("`v'","[0-9]+","")' >> local n `n' `f' >> local n: list uniq n >> } >> di "*** `n' ****" >> reshape long `n', i(id) j(foo) >> >> Two questions: >> 1) Is there a better way to identify stubnames for a -reshape-? >> 2) Is there a more straightforward way to arrive at a unique macrolist >> than the one I chose? In particular, something like the -regexr()- >> function, but with the ability to remove all instances (not just the >> first) of the regular expression. Something like -subinstr()-, but for >> regular expressions. >> * * 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: Selecting stubnames for -reshape- / macrolists***From:*Philipp Rehm <philipp.rehm@gmx.de>

**References**:**st: Selecting stubnames for -reshape- / macrolists***From:*"pr9@duke.edu" <pr9@duke.edu>

**Re: st: Selecting stubnames for -reshape- / macrolists***From:*"E. Paul Wileyto" <epw@mail.med.upenn.edu>

**Re: st: Selecting stubnames for -reshape- / macrolists***From:*Philipp Rehm <philipp.rehm@gmx.de>

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