Dear ExpeRts,
I have trouble implementing a function which computes the k-th derivative of a
specified function f and returns it as a function. I tried to adapt what I
found under ?deriv but could not get it to work. Here is how it should look
like:
## specify the function
f <- function (x,alpha) x^alpha
## higher derivatives
DD <- function(expr, variable, order = 1) {
if(order < 1) stop("'order' must be >= 1")
if(order == 1) deriv(expr, variable)
else DD(deriv(expr, variable), variable, order - 1)
}
## compute the second derivative of f
f.prime.prime <- DD(f,"x",2)
## evaluate it at x=1 for alpha=0.5
f.prime.prime(1,0.5)
Many thanks,
Marius
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