[R] Finding local minima and maxima

[Sean Davis]

I have data in the form of (x,y) pairs and would like to find local 
minima and maxima (typically the zeros of the 2nd derivative) of the y 
values.  I looked at numericDeriv, but I don't have an "expression" per 
se.  I looked at optim, also, but it looks like it will find only one 
"global" max or min.  I can code up my own piecewise derivatives, but 
wondered if there is an existing function to do this.

Thanks,
Sean