create function to solve derivative
On 16-11-2012, at 09:43, e-letter wrote:
On 16/11/2012, Rolf Turner <rolf.turner at xtra.co.nz> wrote:
Your question makes little sense. Functions have derivatives --- at least some of them do. Data sets do not have derivatives. The functions D(), deriv() etc. work on specified analytic expressions for functions --- data sets do not come into the picture.
Is the following procedure correct: Plot data from data set. Suppose the resultant graph was linear. The function could be y=mx+c, so the R function 'lm' could be applied to fit a linear line. The example in the manual for the help file '?D' shows: dx2x <- deriv(~ x^2, "x") ; dx2x So for this example it would be correct to write: functionname<-deriv(~mx+c,"x");dx2x What is the significance of ';dx2x'? It would be appreciated to be referred to the relevant manual sections, thanks.
Manual "Introduction to R" (http://cran.r-project.org/doc/manuals/r-release/R-intro.html) section 2.1 "Vectors and assignment" in particular the sentence: "If an expression is used as a complete command, the value is printed and lost" Berend