[R] Derivative of a function

[Rolf Turner]

(1) You really ought to do your own homework.

(2) What has this to do with R?

     cheers,

         Rolf Turner

On 29/06/11 14:03, Lisa wrote:
> Dear all,
>
> I just want to get the derivative of a function that looks like:
>
> y = exp(x1*b) / (exp(x1*b) + exp(x2*b))
>
> where y is a scalar, x1, x2, and b are vectors. I am going to take the
> derivative of b with respect to y, but I cannot derive an expression in
> which b is function of y. I know there is another way to get the similar
> result, i.e., first take the derivative of y with respect to each element of
> b, and then take its reciprocal. But it is not what I want. Could someone
> please tell me how to solve this problem? Thank you in advance.
>
> Lisa
>
>
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