CrossCat - Forest

CrossCat is a generative model that can be used for categorizing objects given their features. The model assumes that each data point is generated using multiple systems of categories; each such system accounts for some subset of the features.

(define samples

  (mh-query 300 100
  
   (define kind-distribution (DPmem 1.0 gensym))
  
   (define feature->kind
     (mem (lambda (feature) (kind-distribution))))
  
   (define kind->class-distribution
     (mem (lambda (kind) (DPmem 1.0 gensym))))
  
   (define feature-kind/object->class
     (mem (lambda (kind object) ((kind->class-distribution kind)))))
  
   (define class->parameters
     (mem (lambda (object-class) (beta 1 1))))
  
   (define (observe object feature)
     (flip (class->parameters 
             (feature-kind/object->class (feature->kind feature) 
                                         object))))
  
   (list (observe 'spinach 'breakfast)
         (observe 'eggs 'breakfast))
  
   (and (observe 'eggs 'breakfast)
        (observe 'toast 'breakfast)
        (observe 'eggs 'dinner)
        (observe 'spinach 'dinner))))

(hist samples)