[R] create function to solve derivative

[e-letter]

Readers,

A data set comprises

A	B	C
10	6	.2
20	7	.4
30	8	.16
40	9	.0256

My requirement is to obtain the derivative for values of A with
respect to B, create a function in R and plot this derivative against
another variable (e.g. values in column C).

Have searched the mailing list and found reference to a function 'D',
but the help accessed via '?D' and '?deriv' does not explain how to
write a derivative function.

Could someone please direct me to the relevant parts of the manual to begin?

--
R2151