I'm having trouble calculating the Simpson's Diversity Index. I have looked at every possible equation and I keep getting completely different results. I've tried using the whole number of species (i.e. 4 dogs, 3 cats, 6 whatever, etc.) and the proportions to the area (done by dividing population by total number of species) and nothing is working. If anyone knows a fool-proof, useful way to do this I would really appreciate it. Thank you!