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st: prosterior probability and candisc, classification of groups?


From   Allison.Milner@student.griffith.edu.au
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   st: prosterior probability and candisc, classification of groups?
Date   Fri, 08 May 2009 07:52:16 +1000

Dear stata list, 

I have a data set with three groups: other, indig and unknown.
I am trying to predict which proportion of an 'unknown' group is indig using CANDISC. After running Candisc with my grouping variable colour (1indig, 2 other, 3 unknown), I wish to obtain the probability of being 'indig' in the unknown group. 'Do I use estat classtable, prob'? and use the total average posterior probabilities score for 'uknown' as the estimated probability?
here is my syntax:

. candisc   unidepY_N phys_number hangingYN demo1 psych2  le1 le6 le7 le5 le3 le4, 
> group (  indig_other_unknown)

Thanks,
Allison

Canonical linear discriminant analysis

      |                                 | Like- 
      | Canon.   Eigen-     Variance    | lihood
  Fcn | Corr.    value   Prop.   Cumul. | Ratio     F      df1    df2  Prob>F
  ----+---------------------------------+------------------------------------
    1 | 0.2256   .05362  0.6331  0.6331 | 0.9205  35.756    22  1.9e+04 0.0000e
    2 | 0.1736  .031076  0.3669  1.0000 | 0.9699  28.907    10   9302  0.0000 e
  ---------------------------------------------------------------------------
  Ho: this and smaller canon. corr. are zero;                     e = exact F

Standardized canonical discriminant function coefficients

                 | function1  function2 
    -------------+----------------------
       unidepY_N |  -.221696   .0527025 
     phys_number |   .097477   .3828076 
       hangingYN | -.3369913  -.2886416 
           demo1 | -.7805907  -.1454368 
          psych2 | -.0847857   .4737577 
             le1 | -.0384995  -.3522066 
             le6 |  .1490068  -.3371339 
             le7 |  .1222942  -.3227438 
             le5 |  .1619976  -.1516034 
             le3 | -.1707017   -.088264 
             le4 |  -.149231  -.2266881 

Canonical structure

                 | function1  function2 
    -------------+----------------------
       unidepY_N | -.3972627   .4109134 
     phys_number |  -.262388   .2814486 
       hangingYN | -.4214928  -.2506518 
           demo1 | -.8159217  -.1121194 
          psych2 | -.2965078    .502158 
             le1 | -.1772761  -.4004889 
             le6 |  .1362709  -.4429843 
             le7 |  .1036188  -.3933882 
             le5 |    .16394   -.285058 
             le3 | -.2253671  -.2147591 
             le4 | -.1916131  -.2845864 

Group means on canonical variables

    indig_other_ | function1  function2 
    -------------+----------------------
           indig |  .9850372   .0441643 
           other | -.0616017   .0928808 
         unknown | -.0277175  -.3451284 

Resubstitution classification summary

    +---------+
    | Key     |
    |---------|
    | Number  |
    | Percent |
    +---------+
    True         | Classified                         
    indig_other_ |                                    
        unknown  |   indig    other  unknown |   Total
    -------------+---------------------------+--------
           indig |     368       49       69 |     486
                 |   75.72    10.08    14.20 |  100.00
                 |                           |        
           other |   2,069    2,527    2,311 |   6,907
                 |   29.96    36.59    33.46 |  100.00
                 |                           |        
         unknown |     595      418      908 |   1,921
                 |   30.97    21.76    47.27 |  100.00
    -------------+---------------------------+--------
           Total |   3,032    2,994    3,288 |   9,314
                 |   32.55    32.15    35.30 |  100.00
                 |                           |        
          Priors |  0.3333   0.3333   0.3333 |        

. estat classtable if  indig_other_unknown=3, prob
invalid syntax
r(198);

. estat classtable, prob

Average-posterior-probabilities classification table

    +-------------------------------+
    | Key                           |
    |-------------------------------|
    | Number                        |
    | Average posterior probability |
    +-------------------------------+
    True         | Classified                             
    indig_other_ |                                        
        unknown  |   indig    other  unknown  Unclassified
    -------------+----------------------------------------
           indig |     368       49       69             1
                 |  0.5373   0.4650   0.4185              
                 |                                        
           other |   2,069    2,527    2,311            10
                 |  0.4923   0.4990   0.4734              
                 |                                        
         unknown |     595      418      908             3
                 |  0.4797   0.4757   0.4835              
    -------------+----------------------------------------
           Total |   3,032    2,994    3,288            14
                 |  0.4953   0.4952   0.4750              
                 |                                        
          Priors |  0.3333   0.3333   0.3333              




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