-------- Original Message --------
Subject: PGLS troubles
Date: Sun, 24 Feb 2008 17:01:55 +0100
From: [EMAIL PROTECTED]
To: morphmet <[EMAIL PROTECTED]>
Dear morphometrician,
I am Carlo Meloro and I am conducting a research on macroevolutionary
integration in two portions of mammalian carnivore mandible (the
corpus mandibulae and the ascending ramus).
I am wondering if you could give me some suggestions on Partial Least
Square that I am using to validate the possible co-variation between
the two mandible portions.
I have several problems with the results obtained on the same landmark
dataset (separeted in two Blocks: Block 1 = shape variables after GPA
from 9 landmark configurations; Block 2 = shape variables after GPA
from 5 landmark configurations) independently on tpsPLS and Ntsys ver
2.20 N.
There are several discrepancies after the permutation test. Below I
report the output obtained for the same dataset of landmark data for
only 7 specimens. I suppose that there should be a problem of sample
size: do you know any problem associated to sample size in Partial
Least Square analysis?
I appreciate any help to understand this kind of results.
Thank you very much in advance,
Carlo Meloro
Below is the example with a small dataset of 7 specimens:
Results for 7 specimens (Block 1 = 9lnd, Block 2 = 5 lnd) with tpsPLs:
"
Number and percent of squared singular values >= observed
(Expressed as a proportion of the total.)
Dim. Observed Count Percent
1 0.939037 58 5.80%
2 0.049432 921 92.10%
3 0.007188 876 87.60%
4 0.003313 698 69.80%
5 0.000905 549 54.90%
Number and percent of cumulative squared singular values >= observed
(Expressed as a proportion of the total.)
Dim. Observed Count Percent
1 0.939037 58 5.80%
2 0.988470 137 13.70%
3 0.995657 309 30.90%
4 0.998970 422 42.20%
5 0.999876 367 36.70%
HERE THE CUMULATIVE PERCENTAGE DOES NOT APPROACH 100%
Number and percent of correlations >= observed
Dim. Observed Count Percent
1 0.780128 225 22.50%
2 0.479620 873 87.30%
3 0.770183 288 28.80%
4 0.663578 563 56.30%
5 0.615494 683 68.30%
6 0.589321 840 84.00%
"
From this report no correlation between Singular Axis is significant.
[Hide Quoted Text]
Same Results of permutation test from Ntsys:
"
(Note: counts include observed and small percentages imply "significance")
Number and percent of squared singular values >= observed
(Expressed as a proportion of the total.)
Dim. Observed Count Percent
1 0.939037 56 5.60%
2 0.049432 920 92.00%
3 0.007188 837 83.70%
4 0.000905 796 79.60%
5 0.000124 905 90.50%
Number and percent of cumulative squared singular values >= observed
(Expressed as a proportion of the total.)
Dim. Observed Count Percent
1 0.939037 56 5.60%
2 0.988470 130 13.00%
3 0.995657 279 27.90%
4 0.996563 722 72.20%
5 0.996687 801 80.10%
Number and percent of correlations >= observed:
Dim. Observed Count Percent
1 0.780128 51 5.10%
2 0.479620 81 8.10%
3 0.770183 12 1.20%
4 0.615494 92 9.20%
5 0.589321 62 6.20%
6 0.663578 26 2.60%
From this report the correlation obtained for Dimensions 3 and 6 are
significant. The first Dimension approaches significance at 0.05 level
(5.10 %).
Note that there is a large discrepancy in Number and percent of
correlations >= observed from tpsPLS and Ntsys output.
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