Try this:
attributes(eval(df1p))$gradient[,'P']
On Tue, Apr 6, 2010 at 9:09 AM, nickymcp <nickymcpher...@gmail.com> wrote:
>
> I am attempting to extract the derivative/ gradient from this expression
>
> df1p <- deriv(f1, "P")
>> df1p
> expression({
> .value <- s - c - a * P
> .grad <- array(0, c(length(.value), 1L), list(NULL, c("P")))
> .grad[, "P"] <- -a
> attr(.value, "gradient") <- .grad
> .value
> })
>
> So in this case I want to extract the "-a".
>
> I have read the expression help file, which tells me that I should use [ and
> [[ to extract information, but the best result I've had so far is
>
>> df1p[attr(f1,"gradient")]
> expression()
>
> I'm sure I'm missing something really basic, but I've now lost several hours
> trying to do this and I'm getting pretty desperate.
> --
> View this message in context:
> http://n4.nabble.com/Extracting-formulae-from-expression-deriv-tp1752738p1752738.html
> Sent from the R help mailing list archive at Nabble.com.
>
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--
Henrique Dallazuanna
Curitiba-Paraná-Brasil
25° 25' 40" S 49° 16' 22" O
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