Richard Jensen rjensen at SAINTMARYS.EDU
Tue Aug 20 13:15:05 CDT 1996

Regarding the effect of input order on the results of various analyses:

I don't see how the order would have any effect on an eigenanalysis of a
covariance or correlation matrix, as typically used for PCA, or on
eigenanalysis of a dissimilarity matrix as typically used for PCOR.  And,
unless there are programming errors, order of input will have no effect
on the calculation of pairwise similarities or distances.

Order can have an effect on the results of cluster analysis of a
similarity or dissimilarity matrix.  The effect will be a function of how
ties are resolved.  One way around this is to use a program, such as
NTSYS-pc, that will allow the user to find all ties and all solutions -
this can result in many different phenograms for the same data set, just
as there may be many alternative equally parsimonious trees for a data set.

Richard J. Jensen      |   E-MAIL: rjensen at saintmarys.edu
Dept. of Biology       |   TELEPHONE: 219-284-4674
Saint Mary's College   |   FAX: 219-284-4716
Notre Dame, IN  46556  |

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