= statsample-sem

• http://ruby-statsample.rubyforge.org/

== DESCRIPTION:

Structural equation modeling (SEM) for statsample gem, usign ruby and R

== FEATURES/PROBLEMS:

• Abstract generation of models. You could use R packages sem or OpenMx only changing the configuration for engine
• Generates visual representations of output models using GraphViz (to implement)

== SYNOPSIS:

require 'statsample'
require 'statsample/sem'
require 'matrix'

matrix=Matrix[[0.1985443,0.1999953,0.2311884,0.2783865,0.3155943],
[0.1999953,0.2916950,0.2924566,0.3515298,0.4019234],
[0.2311884,0.2924566,0.3740354,0.4061291,0.4573587],
[0.2783865,0.3515298,0.4061291,0.5332788,0.5610769],
[0.3155943,0.4019234,0.4573587,0.5610769,0.6703023]]

cases=500
sem1=Statsample::SEM.new(:name=>"SEM analysis") do |m|
m.data_from_matrix(matrix,:cases=>cases)
m.manifests m.data_variables
m.latents %w{G}
m.path :from=>m.latents, :to=>m.manifests
m.path :from=>m.manifests
m.path :from=>m.latents, :free=>false, :values=>1.0

end
sem1.compute
puts sem1.summary

sem2=sem1.dup
sem2.make_null

sem2.name="Null Model"

sem2.compute

puts sem2.summary

=== OUTPUT

= SEM analysis
  Manifests: VAR1, VAR2, VAR3, VAR4, VAR5
  Latents  : G
  Chi-square: 7.384 (d.f=5)
  Parameter estimation
+------+------+---------------+------------+------------+
| From |  To  |     Label     |  estimate  |     de     |
+------+------+---------------+------------+------------+
| G    | G    | var G (Fixed) | 1.0        | --         |
| G    | VAR1 | G to VAR1     | 0.39715249 | 0.01558258 |
| G    | VAR2 | G to VAR2     | 0.50366170 | 0.01827672 |
| G    | VAR3 | G to VAR3     | 0.57724183 | 0.02049979 |
| G    | VAR4 | G to VAR4     | 0.70277431 | 0.02407548 |
| G    | VAR5 | G to VAR5     | 0.79625084 | 0.02674307 |
| VAR1 | VAR1 | var VAR1      | 0.04081422 | 0.00282540 |
| VAR2 | VAR2 | var VAR2      | 0.03801998 | 0.00281854 |
| VAR3 | VAR3 | var VAR3      | 0.04082727 | 0.00316526 |
| VAR4 | VAR4 | var VAR4      | 0.03938699 | 0.00342167 |
| VAR5 | VAR5 | var VAR5      | 0.03628702 | 0.00369160 |
+------+------+---------------+------------+------------+

= Null Model
  Manifests: VAR1, VAR2, VAR3, VAR4, VAR5
  Latents  : G
  Chi-square: 3725.060 (d.f=10)
  Parameter estimation
+------+------+---------------+------------+------------+
| From |  To  |     Label     |  estimate  |     de     |
+------+------+---------------+------------+------------+
| G    | G    | var G (Fixed) | 1.0        | --         |
| VAR1 | VAR1 | var VAR1      | 0.19854430 | 0.01258228 |
| VAR2 | VAR2 | var VAR2      | 0.29169500 | 0.01847955 |
| VAR3 | VAR3 | var VAR3      | 0.37403540 | 0.02369243 |
| VAR4 | VAR4 | var VAR4      | 0.53327880 | 0.03377395 |
| VAR5 | VAR5 | var VAR5      | 0.67030230 | 0.04244876 |
+------+------+---------------+------------+------------+

== REQUIREMENTS:

• statsample
• R with sem and/or OpenMx packages installed

== INSTALL:

• sudo gem install statsample-sem

== LICENSE:

GPL-2