I'm trying to find shape1 and shape2 in dbeta() such that the answer from dbeta() for the two input values: .6 and .8 become 3.
I'm using the below optim() but don't get exact result, that is I expect getting values for shape1 and shape2 that when used with .6 and .8 give 3 and 3, but they don't, why?
f <- function(x) {
y <- c(3, 3) - dbeta(c(.6, .8), shape1 = x[1], shape2 = x[2])
}
AA = optim(c(1, 1), function(x) sum(f(x)^2), control = list(reltol = (.Machine$double.eps)))
parms = unname(AA$par)
dbeta(c(.6, .8), parms[1], parms[2]) # Here I expect to get `3` for `.6` and `.8` but I don't.