Re: Alscal vs. NCSS
As the other reply suggested, perhaps there is a problem with local maxima. Or maybe, since these are different programs, the commands in one case were incorrect. Why not run a metric MDS for comparison purposes? That might help you decide whether the Alscal or NCSS results are suspect. John Uebersax [EMAIL PROTECTED] [EMAIL PROTECTED] (Niko Tiliopoulos) wrote in message news:<[EMAIL PROTECTED]>... > Dear all, > > I have two questions regarding MDS: > > 1. I have run an NMDS through Alscal (SPSS) and NCSS, and the > representations of the variables on a 2-dimensional map look > completely different. As far as I can tell, I am using the same > procedure in both algorhythms, so I cannot understand why I get > different results, and which one I should prefer as more accurate. > > 2. Does anyone know which of the following two stress indices should > be used with data from psychometric instruments (e.g. personality > questionnaire): > > Kruskal's or Guttman-Lingoes? > > Thank you > > Niko Tiliopoulos = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Re: Alscal vs. NCSS
NMDS can get trapped in local minima. It is advisable to use several random configurations as starting points and choose the solution with the lowest Stress (Kruskal or Young's - I don't have a preference). I checked SPSS and it doesn't have a random initial configuration that I could see. That is an option with the Bell labs KYST-2 program that I use (an old Fortran version) = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
Alscal vs. NCSS
Dear all, I have two questions regarding MDS: 1. I have run an NMDS through Alscal (SPSS) and NCSS, and the representations of the variables on a 2-dimensional map look completely different. As far as I can tell, I am using the same procedure in both algorhythms, so I cannot understand why I get different results, and which one I should prefer as more accurate. 2. Does anyone know which of the following two stress indices should be used with data from psychometric instruments (e.g. personality questionnaire): Kruskal's or Guttman-Lingoes? Thank you Niko Tiliopoulos = Instructions for joining and leaving this list and remarks about the problem of INAPPROPRIATE MESSAGES are available at http://jse.stat.ncsu.edu/ =
