Find x value corresponding to function peak/max in R

Question

I want to find where a function peaks(x value) and not just what the peak value(y value) is, which can be easily done for a range of values, say p.

max(func(p))

Answer 1

Use either one. The 2nd one works if the same max value appears for many p.

p[which.max(func(p))]

p[which(func(p) == max(func(p)))]