Canonical variate analysis biplots - Understanding Biplots - page 190

Ta b l e 4 . 2 1 Class predictivities (weighted and unweighted CVA) obtained with CVA
biplots of the copper froth data.

Weighted CVA

Class 1 Class 2 Class 3 Class 4 Class 5

Dim_1 0.3859 0.4647 0.5444 0.6886 0.9999

Dim_2 0.7463 0.9493 0.8547 0.9919 1.0000

Dim_3 1.0000 1.0000 0.8549 0.9922 1.0000

Dim_4 1.0000 1.0000 1.0000 1.0000 1.0000

Unweighted I CVA

Class 1 Class 2 Class 3 Class 4 Class 5

Dim_1 0.4228 0.4934 0.5249 0.6518 0.9975

Dim_2 0.8156 0.8997 0.9080 0.9707 0.9993

Dim_3 0.9986 0.9938 0.9113 0.9714 0.9994

Dim_4 1.0000 1.0000 1.0000 1.0000 1.0000

Unweighted and centred CVA

Class 1 Class 2 Class 3 Class 4 Class 5

Dim_1 0.4970 0.5436 0.4863 0.5574 0.9999

Dim_2 0.8183 0.8800 0.9611 0.9381 1.0000

Dim_3 0.9999 0.9999 0.9612 0.9383 1.0000

Dim_4 1.0000 1.0000 1.0000 1.0000 1.0000

followed by stage II lower and the most recent from stage II upper. The variables are
as follows:

platfang platform angle;

platfwth platform width;

platfthk platform thickness;

pointlng point length;

pointwdt point width;

pointthk point thickness;

Site MSAI/MSAIIL/MSAIIU;

ratio ratio of point length to platform thickness.

The biplots in Figure 4.23 show that there is a large amount of overlap even
for 0.40-bags. This shows that structurally the data from the three groups cannot
be separated. Even though we cannot separate the three time periods, these biplots
provide the archaeologists with valuable information which can be related to practical
considerations. We see that there is a large part of MSAI towards the right of each
biplot which is completely separated from the MSAII classes. However, part of MSAI
overlaps with the MSAII classes. The MSAII classes show more overlap, with MSAIIU
tending towards the bottom. This can be interpreted as time progression. Tools evolve
over time, with no clear cut-off between the periods. Originally the older MSAI tools
had larger ratio values which reduced over time, that is, the pointlng reduced relative to
platfthk . The overlap indicates that the older MSAI methods were not yet extinct by the