Try this: D(expression(x*x), "x")
On Sat, May 23, 2009 at 12:46 PM, dimitris kapetanakis <[email protected]> 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. > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
