If you want to use "free size effect data" I think it can be good idea use
the residuals of the regression between the PC and log(lengh), because this
residuals are new variables not explained by size.
best
M
2015-10-26 9:42 GMT-03:00 Jens De meyer <[email protected]>:
> Dear,
>
> I have a question about EFDs, and was wondering if you could help me? I
> have performed a PCA on standardized EFDs (standardized for first harmonic,
> using SHAPE-software). The EFDs represented head shapes of eels which were
> given different diets (we compared three different diets). The results of
> the PCA indicated that PC1 was related to variation in head width, with
> high PC-scores being related to broader heads and vice versa. Next, we
> performed a linear regression on these PC-scores and log(length) of the
> three different diets and observed a size-effect in all three diets.
> Because of this, I wanted to divide the PC-scores by the total length of
> the studied eels. Then, we would perform an ANOVA on these length-corrected
> PC-scores between the different diets, as this would allow us to find out
> whether the mean head width of a certain diet is significantly broader than
> another diet.
> Therefore, my question to you is: Am I acutally allowed to divide these
> PC-scores by total length?
> Many thanks in advance!
> Kind regards,
> Jens De Meyer
>
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