-------- Original Message --------
Subject: Re: Variance explained by size
Date: Mon, 29 Aug 2011 11:30:26 -0400
From: Cabo-Perez, Luis <[email protected]>
To: [email protected] <[email protected]>
When you talk about variance explained you are usually referring to
squared correlations. If I am correct, the 99.4% of the component would
be the proportion of total variance explained by the component, which
would be different from the variance of that component explained by
another factor, such as overall size. For one component, the later would
be given by the correlation between the component and centroid size (or
the size measurement relevant for your case) by group. The coefficient
of determination (the square of the correlation coefficient) will then
give you the proportion of the variance of that component explained by
centroid size. In the book's example, a single component accounts for
basically all observed variability (99.4%), and thus in that particular
case you can say that the variances explained are that of overall size
on shape. With more components or lower total variance explained by the
component it would be harder to put it so simply.
Luis
Luis Cabo,
Mercyhurst College,
[email protected]
On Aug 29, 2011, at 10:31 AM, morphmet wrote:
-------- Original Message --------
Subject: Variance explained by size
Date: Fri, 26 Aug 2011 17:29:21 -0400
From: brian boivin <[email protected]>
To: [email protected]
Hi,
In Geometrics morphometrics for Biologist : A Primer (pg7) it says:"In
the two species mentionned above (in which PC1 accounts for 99.4% of
the variance), SIZE explains 71% of the variance in SHAPE in one
species, but only 21.7% in the other."
I did not find any information in the book to explains the impact of
size on the variance in shape. Did I miss something?
How can one calculate the % of variance in shape explained by size?
Email:[email protected]
Thank you for your time
B.B
