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From |
"Alice Dalton (MED)" <[email protected]> |

To |
"[email protected]" <[email protected]> |

Subject |
RE: st: Problem with variables in gllamm |

Date |
Mon, 7 Oct 2013 13:20:21 +0000 |

Dear Statalist, Apologies for omitting information/Stata output from my previous post (I'm new to Statalist and fairly new to Stata). I provide this below. Thanks in advance for your help, Alice - The dependent variable is continuous (a proportion of range 0.0021 to 0.9976) (it measures proportion of overlap between actual and predicted commute routes). - I have 51 participants, each with between 1 and 10 observations (routes) (n=276 in total). - I would like to run a fractional logit model (as I'm using proportions). - I ran this as a gml command initially (glm Overlap50BuffProp Age Health_binaryReversed DistGIS PoI Bike Bus CarBike CarWalk Walk, family(binomial) link(logit) robust) - I'd like to run this in gllamm (so I can model for observations within participants). - I will have just a few predictors (indicated with the glm model as age, health, predicted route distance, points of interest en route, travel mode) - In the Problem 2 example I gave, I replaced the two lowest values with zero then the model worked PROBLEM 1. Dependent variable will only work if the variable contains a zero: a) Where smallest value = 0.0021, model fails . gllamm Overlap50BuffProp, i(Id) family(binomial) link(logit) r(2000); b) Where smallest value = 0 , model works (two values of 0.0021 changed to 0) . gllamm Overlap50BuffPropNoZeros, i(Id) family(binomial) link(logit) Iteration 0: log likelihood = -735.21677 (not concave) Iteration 1: log likelihood = -262.89672 (not concave) Iteration 2: log likelihood = -214.7793 (not concave) Iteration 3: log likelihood = -189.90975 Iteration 4: log likelihood = -181.77366 Iteration 5: log likelihood = -180.63042 Iteration 6: log likelihood = -180.59617 Iteration 7: log likelihood = -180.59616 number of level 1 units = 276 number of level 2 units = 51 Condition Number = 1.2108434 gllamm model log likelihood = -180.59616 ------------------------------------------------------------------------------ Overlap50~os | Coef. Std. Err. z P>|z| [95% Conf. Interval] -------------+---------------------------------------------------------------- _cons | -.48261 .1711324 -2.82 0.005 -.8180232 -.1471967 ------------------------------------------------------------------------------ Variances and covariances of random effects ------------------------------------------------------------------------------ ***level 2 (Id) var(1): .52773855 (.29437029) ------------------------------------------------------------------------------ . PROBLEM 2 Adding binary explanatory variables (0/ 1) into the working model (with zero in dependant variable) . gllamm Overlap50BuffPropNoZeros Health_binaryReversed, i(Id) family(binomial) link(logit) variables have been dropped, can't continue r(198); >-----Original Message----- >From: [email protected] [mailto:owner- >[email protected]] On Behalf Of William Buchanan >Sent: Monday, October 07, 2013 1:31 PM >To: [email protected] >Subject: Re: st: Problem with variables in glamm > >If your dependent variable is binary (like it is implied by the info you provide), >then the only values it should take are 0 & 1. Beyond that it isn't exactly clear >what your specific problem is. You should also include the _exact_ syntax you >enter and the exact message/output provided by Stata. > >Sent from my iPhone > >> On Oct 7, 2013, at 6:53, "Alice Dalton (MED)" <[email protected]> wrote: >> >> Dear Statlist, >> >> I'm having a problem with the gllamm program (family(binomial) link(logit)). >> >> 1. My dependant variable (a proportion) will only work if the variable >contains a zero, otherwise I get an r(2000) (no observations) error >> >> 2. Adding binary explanatory variables (eg a health variable where 1 >excellent, 0 not excellent) results in the message 'variables have been >dropped, can't continue' and an r(198) error. The null model works; the null >model works with continuous variables added in; the null model plus one or >more binary variables fails. >> >> The command I am using is gllamm [depvar] [varlist], i(ParticipantId) >family(binomial) link(logit). I have 276 cases and 129 variables (not all of which >are added to the model). >> >> If anyone with experience of gllamm has an idea of what is happening here, >I would be most grateful to hear it. >> >> Thank you! >> >> Alice Dalton >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/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/faqs/resources/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/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/

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