hello all

I am writing a quite simple script to study dental wear patterns in humans
and I wrote this function

sqrt(var(Y1)+var(Y2))^2-4(var(Y1)*(var(Y2)-cov(Y1,Y2)^2)) but appear this
error message

Error: attempt to apply non-function

alternatively I wrote this
 sqrt(var(Y1)+var(Y2)^2)-4[(var(Y1)*(var(Y2)-cov(Y1,Y2)^2))]

but this error message appear

[1] NA
Warning message:
NAs introduced by coercion

some suggestion to solve this?? thank you so much for your help

Miguel

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