R help - May 2009 - Save values from an expression that is created from deriv command

Dear all,

I want to save a value from an expression that I created by using the deriv
function. So for example the output from an expression using the deriv
command is:

expression({
    .expr7 <- 4 * b.nox.2^2 - 12 * b.nox.3 * b.nox.1
    .expr9 <- -2 * b.nox.2 - sqrt(.expr7)
    .expr10 <- 6 * b.nox.3
    .value <- .expr9/.expr10
    .grad <- array(0, c(length(.value), 1L), list(NULL,
c("b.nox.3")))
    .grad[, "b.nox.3"] <- 0.5 * (12 * b.nox.1 *
.expr7^-0.5)/.expr10 -
        .expr9 * 6/.expr10^2
    attr(.value, "gradient") <- .grad
    .value
})

The problem is that I do not know how to store the:

.grad[, "b.nox.3"] <- 0.5 * (12 * b.nox.1 * .expr7^-0.5)/.expr10 - 
        .expr9 * 6/.expr10^2

and then use its numerical value in my code.

How can I store the above value or any output from the expression from deriv
command so I can use it later in the code?

Any help would be highly appreciated

Thanks

Dimitris
-- 
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Try this:

D(expression(x*x), "x")


On Sat, May 23, 2009 at 12:46 PM, dimitris kapetanakis
<gamitor at gmail.com> wrote:
>
> Dear all,
>
> I want to save a value from an expression that I created by using the deriv
> function. So for example the output from an expression using the deriv
> command is:
>
> expression({
> ? ?.expr7 <- 4 * b.nox.2^2 - 12 * b.nox.3 * b.nox.1
> ? ?.expr9 <- -2 * b.nox.2 - sqrt(.expr7)
> ? ?.expr10 <- 6 * b.nox.3
> ? ?.value <- .expr9/.expr10
> ? ?.grad <- array(0, c(length(.value), 1L), list(NULL,
c("b.nox.3")))
> ? ?.grad[, "b.nox.3"] <- 0.5 * (12 * b.nox.1 *
.expr7^-0.5)/.expr10 -
> ? ? ? ?.expr9 * 6/.expr10^2
> ? ?attr(.value, "gradient") <- .grad
> ? ?.value
> })
>
> The problem is that I do not know how to store the:
>
> .grad[, "b.nox.3"] <- 0.5 * (12 * b.nox.1 *
.expr7^-0.5)/.expr10 -
> ? ? ? ?.expr9 * 6/.expr10^2
>
> and then use its numerical value in my code.
>
> How can I store the above value or any output from the expression from
deriv
> command so I can use it later in the code?
>
> Any help would be highly appreciated
>
> Thanks
>
> Dimitris
> --
> View this message in context:
http://www.nabble.com/Save-values-from-an-expression-that-is-created-from-deriv-command-tp23686186p23686186.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
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