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

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

Subject |
st: RE: RE: RE: mapping a value from 2 variables |

Date |
Fri, 26 Jul 2002 12:52:54 +0100 |

Joly.Patrick@ic.gc.ca > > To recap this thread: In response to my posting where I > expressed my wish > to avoid explicit looping over observations to create a > value label mapping > between a numeric variable and a string variable, Michael > Blasnik suggested > the following approach: < snip > > > Nick Cox had previously suggested < snip > > > To compare the relative efficiency of both solutions, I put > together two > separate routines, one using the -forvalue- approach, the > other using the > -outsheet- line. I then compared their relative > performance (see table > below). < snip > > > maplab2 turned out to be much faster! It's running the .do > file in in > maplab1 which is time consuming. Here's a quick tabulation > > seconds elapsed > ---------- > obs ('000s) maplab1 maplab2 > ------------+---------------------- > 1 | .3 .2 > 3 | 1.1 1.3 > 5 | 4.7 2.7 > 7 | 11.6 4.2 > 9 | 21.8 5.6 > 30 | 300.3 21.2 > > where we have a different value label for each observation. > > I'll go with maplab2 then. Thanks all. > I'll add two comments: one is trivial and the other is less so. 1. Anyone wanting to copy Patrick's program -maplab2- should note that he has left wired into three lines his original variable names > local val = naics[`i'] > local label = labelnaics[`i'] > label def naicslab `val' "`label'" , modify The correction is just to generalise to use `1', `2' and `labname'. 2. The results seem fairly clearcut, but I'll repeat an earlier caution that even relative timings dependent on I/O can vary according to machine, OS and set-up (e.g. whether you are using Stata on your "own" machine or over a network). In preparing an FAQ on a different question which is at http://www.stata.com/support/faqs/data/savesome.html and trying to distill which method of two was faster, Paul Seed, Jean Marie Linhart and I found what were to me surprising contradictions, with my "own" Stata 7 under Windows XP being the odd one out. 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/

**References**:**st: RE: RE: mapping a value from 2 variables***From:*Joly.Patrick@ic.gc.ca

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