比较各椭圆（生态位）面积的显著性差异 Compare two ellipses for significant differences in SEA.
To test whether Group 1 SEA is smaller than Group 2…
You need to calculate the Proportion of G1 ellipses that are less than G2.
#in this case,all the posterior ellipses for G1 are less than G2 so we can conclude that G1 is smaller than G2 with p approx=0,and certainly p<0.0001.
#and for G1<G3
计算椭圆（生态位）之间的重复面积和重复百分比 To calculate the overlap between two ellipses you can use the following code
# NB: the degree of overlap is sensitive to the size of ellipse you choose to draw around each group of data. However, regardless of the choice of ellipse, the extent of overlap will range from 0 to 1, with values closer to 1 representing more overlap. So, at worst it is a semi-quantitative
# measure regardless of extent of the ellipse, but the finer detials and magnitudes of the effect size will be sensitive to this choice.
# Additional coding will be required if you wish to calculate the overlap between ellipses other than those described by SEA or SEAc.
# Fit a standard ellipse to the data, NB, I use a small step size to make sure i get more "round" ellipses, as this method is computatonal and based on the discretisation of the ellipse boundaries.
# The overlap between the SEAc for groups 1 and 3 is given by:
# One can calculate the overlap between two (or more) ellipses. In the first instance, this overlap is simply the area, #in units of per mil squared, contained by the shape that lies within the overlapping region.
# This overlapis most easily calculated by using the SEAc of each ellipse.
One might then wish to calculate the proportion overlap; athough one then runs into a choice as to what the demoninator will be in the equation. You could for instance calculate
the proportion of A that overlaps with B,
the proporiton of B that overlaps with A,
or the proportion of A and B that overlap with each other.