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From |
Suzy <[email protected]> |

To |
[email protected] |

Subject |
Re: Antwort: st: why is a category being dropped by Stata? |

Date |
Mon, 11 Jul 2005 11:33:32 -0400 |

When I include the nocons syntax, I get the same problem, but now with the c_n_demo_1 dummy is dropped. BTW, I've run quite a few regressions using the xi: comman with other datasets and this has never happened before. (I tried a regression without including on 1-1145 observations and Stata drops c_n_demo_2, like without the nocons syntax when I kept in the 1/1145.

xi: regress ln_pbb demo_yn i.c_n_demo newrace2 bldyr_pp i.age_cat sex2 in 1/1145, nocons

------------------------------------------------------------------------------

ln_pbb | Coef. Std. Err. t P>|t| [95% Conf. Interval]

-------------+----------------------------------------------------------------

demo_yn | .0744378 .0483279 1.54 0.124 -.020384 .1692596

_Ic_n_demo_1 | (dropped)

_Ic_n_demo_2 | .2674317 .1162665 2.30 0.022 .0393109 .4955525

newrace2 | .541398 .0552086 9.81 0.000 .433076 .64972

bldyr_pp | .6846982 .0580307 11.80 0.000 .5708389 .7985574

_Iage_cat_1 | .6328892 .0603672 10.48 0.000 .5144456 .7513327

_Iage_cat_2 | .4941141 .0600306 8.23 0.000 .3763311 .6118971

sex2 | .1092572 .0396376 2.76 0.006 .0314863 .1870282

------------------------------------------------------------------------------

Hans J. Baumgartner wrote:

Hi Suzy,

the xi indcatvargenerates dummies for each category. Since you did not use the nocons option, one dummy has to be dropped. Otherwise the dummies were perfectly collinear with the constant, since they add up to unity. So everything is correct and the coefficient on _I_indcatvar should be interpreted relative to the dummy-base.

Hans

[email protected] schrieb am 11/07/2005 14:30:20:

Dear Statamembers,*

I have a categorical variable, coded as 0, 1, 2.

When I do a a simple regression equation using "xi: regress depvar, indcontvar, i.indcatvar, "

Stata drops the category 2 (n=40/1196)

I have other categorical variables in the model, but everything else looks OK.

I have no idea why it's being dropped.

thanks for any insight.

Suzy

*

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**References**:**Antwort: st: why is a category being dropped by Stata?***From:*"Hans J. Baumgartner" <[email protected]>

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