Thanks for the response. Yes, I did study the vignette but did not understand it fully. Anyway, I have tried once again now. I am happy to say that I have got what I wanted.
library(Ryacas) x <- Sym("x");U <- Sym("U");x0 <- Sym("x0");C <- Sym("C") my_func <- function(x,U,x0,C) { return (U/(1+exp(-(x-x0)/C)))} FirstDeriv <- deriv(my_func(x,U,x0,C), x) PrettyForm(FirstDeriv) #slope <- yacas("Subst(x,x0),deriv(my_func(x,U,x0,C), x)") slope <- Subst(FirstDeriv,x,x0) #PrettyForm(slope) - gives errors PrettyForm(Simplify(slope)) I was confused by the references to the yacas command. Now, I have chosen to omit it. Then I get what I want. Thanks, Vivek 2017-09-19 16:04 GMT+02:00 Bert Gunter <bgunter.4...@gmail.com>: > Have you studied the "Introduction to Ryacas" vignette that come with the > package? > > Cheers, > Bert > > > > Bert Gunter > > "The trouble with having an open mind is that people keep coming along and > sticking things into it." > -- Opus (aka Berkeley Breathed in his "Bloom County" comic strip ) > > On Tue, Sep 19, 2017 at 2:37 AM, Vivek Sutradhara <viveksu...@gmail.com> > wrote: > >> Hi all, >> I am trying to implement the following matlab code with Ryacas : >> >> syms U x x0 C >> >> d1=diff(U/(1+exp(-(x-x0)/C)),x); >> >> pretty(d1) >> >> d2=diff(U/(1+exp(-(x-x0)/C)),x,2); >> >> pretty(d2) >> >> solx2 = solve(d2 == 0, x, 'Real', true) >> >> pretty(solx2) >> >> slope2=subs(d1,solx2) >> >> >> I have tried the following : >> >> library(Ryacas) >> >> x <- Sym("x");U <- Sym("U");x0 <- Sym("x0");C <- Sym("C") >> >> my_func <- function(x,U,x0,C) { >> >> return (U/(1+exp(-(x-x0)/C)))} >> >> FirstDeriv <- deriv(my_func(x,U,x0,C), x) >> >> PrettyForm(FirstDeriv) >> >> slope <- yacas("Subst(x,x0),deriv(my_func(x,U,x0,C), x)") >> >> PrettyForm(slope) >> >> >> I don't understand how I should use the Subst command. I want the slope of >> the first derivative at x=x0. How do I implement that? >> >> I would appreciate any help that I can get. >> >> Thanks, >> >> Vivek >> >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see >> https://stat.ethz.ch/mailman/listinfo/r-help >> PLEASE do read the posting guide http://www.R-project.org/posti >> ng-guide.html >> and provide commented, minimal, self-contained, reproducible code. >> > > [[alternative HTML version deleted]] ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.