Dear Callie,

`I am not sure I fully understand your question. Perhaps you could`

`provide details as to how your 20 projectile points are transformed into`

`data, how the pairwise rotation of two configurations was applied to`

`your 20 projectile points, and what is the aim of the test.`

`Now, let's assume for the sake of argument that you have converted your`

`projectile points into data as a set of n 2D landmarks (in the case of`

`circle you would have used the same amount of points to form a circle).`

`Let's also assume that you have used as starting point for your PROTEST`

`two of these configuration of landmarks (i.e., the matrix with n rows`

`and 2 columns containing the x,y coordinates of each landmark; one`

`matrix for one projectile point, the other for another projectile point).`

`If the above were true and based on the way the procedure works (in my`

`case, I'm referring to the description in Peres-Neto & Jackson 2001 -`

`Oecologia), I think a reasonable expectation, for two quite similar`

`shapes, would be:`

`- that after Procrustes superimposition, the x,y coordinates of`

`corresponding points/landmarks would be extremely similar, giving a very`

`low "Procrustes sum of squares (m12)"`

`- that randomly exchanging the order of the points in one of the two`

`configurations would basically never give you a "Procrustes sum of`

`squares (m12)" as small (because, in lay terms, if in one of the two`

`landmark configurations you exchange the position of two or more of the`

`landmarks, the two shapes will not match as precisely as your original`

`configuration)`

`Blake has given you a potential explanation of why a specific value,`

`perhaps my hypothetical scenario (if it applies) can give you a hint on`

`why that is always the same.`

`If the hypothetical scenario above were correct, I would see no special`

`issue with the value being always the same (and extremely low). In that`

`case, however, there might be an issue with the practical utility of`

`performing the test in the first place.`

I hope this helps, Carmelo Il 16/01/2018 7:51 PM, Callie Diduck ha scritto:

Hi,I am wondering if any one can help me. I have been running a ProcrustesRotation of Two Configurations and PROTEST using the vegan package in R.The Procrustes seem to be working but I am having an issue with theresults of the PROTEST and the correlation values.I am getting identical p values every time I run the script. I have asample size of 20 projectile points and every time I run the statisticsmy p value isequal to 0.00009999. I ran a test and I compared a circle to one of myprojectile points and I still got a p value of 0.00009999.Here are the results for the test of the projectile point compared to acircle:Procrustes sum of squares: 1.817e+04 Call: protest(X = p730, Y = pTest, permutations = 10000) Procrustes Sum of Squares (m12 squared): 0.06296 Correlation in a symmetric Procrustes rotation: 0.968 Significance: 9.999e-05 Permutation: free Number of permutations: 10000If anyone has any idea of why this could be happening or how to fix itthat would be greatly appreciated.Thanks Callie Diduck -- MORPHMET may be accessed via its webpage at http://www.morphometrics.org ---You received this message because you are subscribed to the GoogleGroups "MORPHMET" group.To unsubscribe from this group and stop receiving emails from it, sendan email to morphmet+unsubscr...@morphometrics.org<mailto:morphmet+unsubscr...@morphometrics.org>.

-- MORPHMET may be accessed via its webpage at http://www.morphometrics.org

`---`

`You received this message because you are subscribed to the Google Groups "MORPHMET" group.`

To unsubscribe from this group and stop receiving emails from it, send an email to morphmet+unsubscr...@morphometrics.org.