[R-sig-eco] mantel missing data

2010-02-11 Thread Dan Rabosky

Howdy-

Any thoughts on testing associations between distance matrices with 50% 
missing data? A standard mantel test is inadequate, as it leads to many 
pairings between missing  non-missing values. For the particular problem of 
interest, I can't randomize the raw data used to compute the distance matrices, 
because it is the distances themselves that are measured (e.g., frequency of 
hybridization between two species). 

What about randomizing the data (not row-column permutations), and using 
simulations with an identical missing-data structure to assess the Type I error 
rates? Seems like a crude method to check whether failing to account for 
within-row or within-column covariances is likely to be problematic, given the 
level of missing data, but I don't have any other ideas.

Cheers,
~Dan Rabosky
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[R-sig-eco] mantel missing data

2010-02-10 Thread Dan Rabosky


Howdy-

Any thoughts on testing associations between distance matrices with 50% 
missing data? A standard mantel test is inadequate, as it leads to many 
pairings between missing  non-missing values. For the particular problem of 
interest, I can't randomize the raw data used to compute the distance matrices, 
because it is the distances themselves that are measured (e.g., frequency of 
hybridization between two species). 

What about randomizing the data (not row-column permutations), and using 
simulations with an identical missing-data structure to assess the Type I error 
rates? Seems like a crude method to check whether failing to account for 
within-row or within-column covariances is likely to be problematic, given the 
level of missing data, but I don't have any other ideas.

Cheers,
~Dan Rabosky




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