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decuslib20-02
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decus/20-0026/dmatx.doc
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SUBROUTINE DMATX
PURPOSE
COMPUTE MEANS OF VARIABLES IN EACH GROUP AND A POOLED
DISPERSION MATRIX FOR ALL THE GROUPS. NORMALLY THIS SUB-
ROUTINE IS USED IN THE PERFORMANCE OF DISCRIMINANT ANALYSIS.
USAGE
CALL DMATX (K,M,N,X,XBAR,D,CMEAN)
DESCRIPTION OF PARAMETERS
K - NUMBER OF GROUPS
M - NUMBER OF VARIABLES (MUST BE THE SAME FOR ALL
GROUPS).
N - INPUT VECTOR OF LENGTH K CONTAINING SAMPLE SIZES OF
GROUPS.
X - INPUT VECTOR CONTAINING DATA IN THE MANNER EQUIVA-
LENT TO A 3-DIMENSIONAL FORTRAN ARRAY, X(1,1,1),
X(2,1,1), X(3,1,1), ETC. THE FIRST SUBSCRIPT IS
CASE NUMBER, THE SECOND SUBSCRIPT IS VARIABLE NUMBER
AND THE THIRD SUBSCRIPT IS GROUP NUMBER. THE
LENGTH OF VECTOR X IS EQUAL TO THE TOTAL NUMBER OF
DATA POINTS, T*M, WHERE T = N(1)+N(2)+...+N(K).
XBAR - OUTPUT MATRIX (M X K) CONTAINING MEANS OF VARIABLES
IN K GROUPS.
D - OUTPUT MATRIX (M X M) CONTAINING POOLED DISPERSION.
CMEAN - WORKING VECTOR OF LENGTH M.
REMARKS
THE NUMBER OF VARIABLES MUST BE GREATER THAN OR EQUAL TO
THE NUMBER OF GROUPS.
SUBROUTINES AND FUNCTION SUBPROGRAMS REQUIRED
NONE
METHOD
REFER TO 'BMD COMPUTER PROGRAMS MANUAL', EDITED BY W. J.
DIXON, UCLA, 1964, AND T. W. ANDERSON, 'INTRODUCTION TO
MULTIVARIATE STATISTICAL ANALYSIS', JOHN WILEY AND SONS,
1958, SECTION 6.6-6.8.