>You seem a trifle sensitive about models and modeling - statistics >are just tools.
Fully agree......but these tools that have to be applied correctly. > It makes no sense to say that something is wrong with the data. I see data sets all the time that are wrong; mistakes, typos, wrong coding of categorical variables, blanks, improper variable names, etc, etc. These can make a GLM routine crash. >Either the program works for its intened purpose or it doesn't. Here is another reason for non-convergence: models with interactions applied on highly unbalanced data; not enough observations in a particular two- or three way interaction combination. >If one of the statisticians who helped debug the program for SAS and >another professional statistician/programmer cannot get the program >to work with a data set I'd say that the functionality of of the >algorithm depends on the data set - it is a tool that sometimes >can't handle the data. Improper application of a particular method, over-complicated models with too many parameters, or "funny" things with the data comes to my mind first. I have even seen people applying a Poisson GLM on negative data, and wondering why it crashed. Perhaps you are willing to upload your data to a website, so that we can all have a go at it? That would solve this discussion for once and for all. Else we will never know why, and how you managed to crash the GLM routine in SAS. Alain Dr. Alain F. Zuur First author of: Analysing Ecological Data (2007). Zuur, AF, Ieno, EN and Smith, GM. Springer. 680 p. URL: www.springer.com/0-387-45967-7 Analysing Ecological data using GLMM and GAMM in R. (2008). Zuur, AF, Ieno, EN, Walker, N and Smith, GM Springer. Other books: http://www.brodgar.com/books.htm Statistical consultancy, courses, data analysis and software Highland Statistics Ltd. 6 Laverock road UK - AB41 6FN Newburgh Tel: 0044 1358 788177 Email: [EMAIL PROTECTED] URL: www.highstat.com URL: www.brodgar.com
