# symbolic computing example with Ryacas

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## symbolic computing example with Ryacas

 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]] ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.
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## Re: symbolic computing example with Ryacas

 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 <[hidden email]> 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]] > > ______________________________________________ > [hidden email] 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. >         [[alternative HTML version deleted]] ______________________________________________ [hidden email] mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-helpPLEASE do read the posting guide http://www.R-project.org/posting-guide.htmland provide commented, minimal, self-contained, reproducible code.