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From |
fgallo@wnec.edu |

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<statalist@hsphsun2.harvard.edu> |

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

Date |
Sun, 5 Oct 2008 19:28:38 -0400 |

Thank you all very much for responding with your thoughts and suggestions. Best, Frank On Sun 05/10/08 3:26 PM , Steven Samuels sjhsamuels@earthlink.net sent: > Agreed. > > > > -Steve > > On Oct 5, 2008, at 1:11 PM, Nick Cox wrote: > > > > > 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/ > > > * > > * 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/ > > > > * * 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/

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