Discriminant function analysis

Posted by Pete on Apr 20, 2011; 8:33am
URL: http://spssx-discussion.165.s1.nabble.com/Discriminant-function-analysis-tp4315226.html

I've done a discriminant function analysis in SPSS intended to classify 3 types of case using 30 variables. The discriminant function coefficients and structure matrix are below. It is clear that the two functions do different things with these data. I have the following questions:
1. How do I identify what each function is doing when cases are classified?
2. I want to calculate on a case by case basis the scores for truncated forms of each discriminant function (f1 S1DUR - S3PIRANG and f2 S3INRANG -RPVIS1). I assume I generate a linear equation using these coefficients to weight each variable. Is that right?
3. Alternatively, is there a simple way of obtaining the scores from each case for each discriminant function by procedures in SPSS? On reflection, this might be the preferred option, but I will stand to be advised.

any other advice, observations would be gratefully received.
Many thanks
PH


Standardized Canonical Discriminant Function Coefficients
  Function
        1 2
S1DUR .106 -.090
S1PIRANG -.041 .074
S1INRENG .087 .009
S2DUR -.048 -.276
S2PIRANG .198 -.284
S2INRANG .211 -.113
S3DUR -1.906 .829
S3PIRANG .034 .016
S3INRANG .273 .437
S4DUR 1.546 -.843
S4PIRANG .123 .118
S4INRANG -.326 -.145
NPVIS1 -.246 -.002
NPVIS2 -.165 .343
NPVIS3 .096 -.201
RPVIS4 .253 .362
NPVIS4 .373 -.099
RPVIS1PI -.250 .234
RPVIS2PI .256 .345
RPVIS3PI .067 .107
RPVIS4PI .081 -.113
RPVIS1IN .061 .316
RPVIS2IN -.689 -.097
RPVIS3IN .640 -.269
RPVIS4IN .229 .239
RPVI1TO4 -.200 1.226
NPVI1TO4 .082 -1.588


Structure Matrix
  Function
        1 2
NPVIS4 .324 -.053
S4INRANG -.255 -.014
S2INRANG .245 .076
RPVIS3IN .230 -.029
S3DUR -.227 -.065
RPVIS3 -.227 -.065
NPVIS1 -.222 .047
S4DUR -.155 -.079
RPVIS2IN -.119 .068
S2DUR -.117 .012
RPVIS2 -.117 .012
RPVIS4PI .106 .053
RPVIS4 .103 .047
S1INRENG -.100 -.034
S3PIRANG .088 -.038
RPVI1TO4 -.077 .057
S4PIRANG .072 .049
S3INRANG .141 .354
RPVIS3PI .040 .318
RPVIS2PI .175 .313
NPVIS2 -.210 .306
RPVIS1PI -.124 .225
S2PIRANG .078 -.207
RPVIS4IN .119 .181
NPVI1TO4 -.064 -.168
NPVIS3 .111 -.167
RPVIS1IN .144 .158
S1PIRANG .069 -.082
S1DUR .033 -.062
RPVIS1 .033 -.062
Pooled within-groups correlations between discriminating variables and standardized canonical discriminant functions
 Variables ordered by absolute size of correlation within function.
* Largest absolute correlation between each variable and any discriminant function
a This variable not used in the analysis.