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From |
Allan Reese <R.A.Reese@hull.ac.uk> |

To |
Stata distribution list <statalist@hsphsun2.harvard.edu> |

Subject |
Re: st: RE: Taking averages, etc. |

Date |
Wed, 17 Dec 2003 12:38:22 +0000 (GMT) |

On Wed, 17 Dec 2003, Richard Williams wrote: > In SPSS, I could do something like > > DO IF X1 = 1 and X2 = 3 > Compute Y = 3. > ELSE IF X3 = 2 and X4 = 17 > Compute Y = 4. > ELSE > Compute Y = 5. > END IF. ... > In stata, ... > gen y = 3 if X1==1 & X2==3 > replace y = 4 if X1 !=1 & X2 !=3 & X3==2 & X4==17 > replace y = 5 if X1 !=1 & X2 !=3 & X3 !=2 & X4 !=17 First point is to analyse the logic. Reforming a problem often speeds up the execution far more than fancy coding, and leads to insights. In this case: gen y=5 replace y=3 if x1==1 & x2==3 replace y=4 if y==5 & (x3==2 & x4==17) performs far fewer tests. The parentheses do not affect the result but emphasise the logic. Stata, as Nick has already replied, has a completely general control language that includes if/then/else, for and while. Unlike SPSS, where only data transformations can be put into DO IF and LOOP constructions, Stata allows any statements or blocks of statements. These may conveniently be written using an editor (provided it doesn't add a file extension!) and saved as .DO or .ADO on the fly. R. Allan Reese Email: r.a.reese@hull.ac.uk Associate Manager GRI Direct voice: +44 1482 466845 Graduate School Voice messages: +44 1482 466844 Hull University, Hull HU6 7RX, UK. Fax: +44 1482 466436 ==================================================================== Be careful in handling the battery of the remote control transmitter If swallowed consult a physician immediately for emergency treatment [Safety instructions: Hitachi CP-X275 data projector] * * 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: Taking averages, etc.***From:*Richard Williams <Richard.A.Williams.5@nd.edu>

**Re: st: RE: Taking averages, etc.***From:*Richard Williams <Richard.A.Williams.5@nd.edu>

**References**:**Re: st: RE: Taking averages, etc.***From:*Richard Williams <Richard.A.Williams.5@nd.edu>

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