Hi,

I'm trying to use Pearson's Chi-squared to verify the dependence among
species distribuion.

I have a dataframe with the presence/absence data of two species in a
number of sample units

The equation I'm using is:

X2= p*(|ad-bc|-p/2)^2 / ((a+b)*(c+d)*(a+c)*(b+d))

where a is the number of double presence (1-1), b is the number of 1-0, c
is the number of 0-1 and d is the number of 0,0 (double absence)
p is a+b+c+d

Is there a function to caltulate it using R? I could not understand how to
use chisq.test function for this.

Thanks in advance.

Antonio Olinto

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