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

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

Subject |
RE: st: Identify Categorical/Dichotomous and Continuous Variables |

Date |
Sun, 5 Oct 2008 18:11:22 +0100 |

Good advice, but to repeat for Frank and any others puzzled: Stata does not think of such variables as nominal, indicator, etc. If something is (say) coded 0, 1 or missing then any user is perfectly entitled to think of it as an indicator/dummy, etc., but Stata does not think that way. It's in your mind, not Stata's. Nick n.j.cox@durham.ac.uk Steven Samuels To turn any variable in Stata into a nominal variable, you create indicator variables. This is what SPSS does when you use a categorical variable as a predictor in regression. There are two ways of doing this in Stata: a) -xi- or b) -tab- with the -gen()- option. See http://www.ats.ucla.edu/stat/Stata/webbooks/reg/chapter3/ statareg3.htm Section 3.3 for some examples. On Oct 5, 2008, at 12:33 PM, Nick Cox wrote: > This is not quite true. In particular, -anova- has an idea of the > distinction. If you specify that a variable is categorical or > continuous, or imply that by default, -anova- takes action > accordingly. > > But in general, as others have emphasised or implied, Stata puts the > onus on users to decide how they want variables to be treated. If you > want -foreign- in the auto data to be a binary response for -logit-, > that's fine. If you want to average it with -summarize-, that's fine > too. Sometimes, Stata will refuse to do something on principle; more > usually, it assumes that you are smart enough to know what you want to > do. > > # of distinct values is, as Svend will agree, a criterion to be used > circumspectly. I often deal with rainfall data usually measured by > convention to a resolution of 0.1 mm. I bet that the number of > distinct > values met in practice is fewer than that in the typical > classifications > of death, disease or economic activity. > > Nick > n.j.cox@durham.ac.uk > > Svend Juul > > As Martin responded: Stata has no formal distinction between > continuous and categorical numeric variables. However, the > command > > codebook, compact > > may tell you what you want. The -Unique- column tells you > how many "unique" (meaning different) values each variable > has. > > Frank > > I am new to Stata: moved from SPSS a week ago. I am hoping > that someone can help me with what I imagine is a simple > issue. I saved an SPSS file as a Stata one. I am working > my way through the user guide and the data management > manual, but I am having difficulty with confirming whether > Stata recognizes variables as continuous (or scale) or > categorical/dichotomous (or nominal). In SPSS, you can > easily identify whether the type of measure is a scale, > nominal, or string with its drop down menu in the variable > view. It would be a great help, and I would appreciate it > very much if someone would tell me the method to confirm > the data type for categorical/dichotomous and for > continuous variables? Thank you. * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/statalist/faq * http://www.ats.ucla.edu/stat/stata/

**Follow-Ups**:**Re: st: Identify Categorical/Dichotomous and Continuous Variables***From:*Steven Samuels <sjhsamuels@earthlink.net>

**References**:**Re: st: Identify Categorical/Dichotomous and Continuous Variables***From:*Svend Juul <SJ@SOCI.AU.DK>

**RE: st: Identify Categorical/Dichotomous and Continuous Variables***From:*"Nick Cox" <n.j.cox@durham.ac.uk>

**Re: st: Identify Categorical/Dichotomous and Continuous Variables***From:*Steven Samuels <sjhsamuels@earthlink.net>

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