symbolic computing example with Ryacas

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symbolic computing example with Ryacas

vivek
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

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Re: symbolic computing example with Ryacas

Bert Gunter-2
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]]

______________________________________________
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Re: symbolic computing example with Ryacas

vivek
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 <[hidden email]>:

> 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/posti
>> ng-guide.html
>> and provide commented, minimal, self-contained, reproducible code.
>>
>
>

        [[alternative HTML version deleted]]

______________________________________________
[hidden email] mailing list -- To UNSUBSCRIBE and more, see
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and provide commented, minimal, self-contained, reproducible code.
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Re: symbolic computing example with Ryacas

Gabor Grothendieck
Here are some more examples:

library(Ryacas)

x <- Sym("x")
yacas("x:=2")
Eval(x*x)
## [1] 4

# vignette has similar example
y <- Sym("y")
Eval(Subst(y*y, y, 3))
## [1] 9

# demo("Ryacas-Function") has similar example to this
f <- function(z) {}
body(f) <- yacas(expression(z*z))[[1]]
f(4)
## [1] 16



On Tue, Sep 19, 2017 at 2:08 PM, Vivek Sutradhara <[hidden email]> wrote:

> 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 <[hidden email]>:
>
>> 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/posti
>>> ng-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-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.



--
Statistics & Software Consulting
GKX Group, GKX Associates Inc.
tel: 1-877-GKX-GROUP
email: ggrothendieck at gmail.com

______________________________________________
[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.