Ha! Even better - thank you. Plenty here for me to play around with.
Many thanks
Andrew
On 23/09/18 15:22, Michael Friendly wrote:
On 9/22/2018 6:49 AM, Andrew wrote:
Hi Michael
This looks like it could be really helpful in moving my project
forwards thank you.
I remember many years ago using (proprietary) software from the
University of Liverpool which did a nice job of allowing regions to
be defined, and then for the space to be rotated to obtain visual
inspection of relative distance from different angles. I appreciate
that smacof will not do that, but as long as the analysis allows for
the graph to be plotted and analysed, that's what's important.
You need not rely on the plots provided directly by a given package.
Just roll your own using standard plotting libraries.
Here is just the first Google hit on "R MDS 3D plot"
http://omnilogia.blogspot.com/2014/05/basic-2d-3d-multi-dimensional-scaling.html
which shows a rotating 3D plot, colored by a grouping variable. Here
is another:
http://whatzcookinlab.blogspot.com/2013/05/spinning-3d-mds-plot.html
The vegan and ade4 packages also have a variety of plots and related
methods.
-Michael
Thank you again, and to all of those who responded.
Best wishes
Andrew
On 21/09/18 14:07, Michael Friendly wrote:
Smallest space analysis (SSA) is just the name given to software
developed by Guttman & Lingoes around the time the various versions
of multidimensional scaling were being developed. Call it Israeli MDS
or Falafel MDS if you prefer. The reason you encountered it in your
course is presumably that the instructor was trained in that.
There are several variants of MDS-like algorithms for embedding
points representing objects in a space, using data representing
similarities or distances among objects -- metric (cmdscale)
and non-metric (MASS::isoMDS), using only rank order information,
and a variety of
measures of goodness-of-fit ("stress"). I don't recall the details
of the SSA programs, but that should matter little conceptually.
The smacof package offers the widest array of possibilities.
-Michael
On 9/19/2018 7:00 AM, Andrew wrote:
Hi
As part of my forensics psych course, we have been introduced to
Guttman's smallest space analysis (SSA). I want to explore this
approach
using R, but despite finding some queries on the web about this same
thing, have yet to find any answers. The MASS package doesn't seem
to do
the job, and the only thing I have been able to find is some
proprietary
software HUDAP (Hebrew University Data Analysis Package) which
may/ not
be compatible with R (or GNU/Linux for that matter).
Does anyone have information on how to do SSA using R?
Many thanks
Andrew
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