[R] How does once import a function from an imported script?

[R. Michael Weylandt]

Going down the text parsing approach, you might want to use something
like this:

fnc <- eval(parse(text="function(x) dnorm(x)"))

all.equal(1/sqrt(2*pi), fnc(0))
[1] TRUE

On Thu, Nov 10, 2011 at 8:55 AM, David Winsemius <dwinsemius at comcast.net> wrote:
>
> On Nov 9, 2011, at 9:11 PM, Aimee Jones wrote:
>
>> Hi all,
>> I am trying to import some functions into a script and am having
>> difficulty in doing so. I am able to import a series of functions from
>> a .tex file into my script, and call on each function by column name,
>> however R reads them as data rather than as functions and I am
>> struggling with the syntax to make R read them as a function instead.
>>
>> Below is a small set of the things I have tried:
>>
>> parms["B1"]
>>
>> returns the character string {2*dnorm(T1(t),mean=32.5,sd=7)} . This is
>> from the imported script "parms".
>>
>> when I write B1<-function(T1,t) (parms["B1"]) and then enter B1 to see
>> what the workspace returns, I get
>>
>> function(T1,t) (parms["B1"])
>>
>> I am trying to get B1 to return as function(T1,t)
>> {2*dnorm(T1(t),mean=32.5,sd=7)}, so that I can plot B1(T1,t).
>
> You need to use the proper functions to transmute character values to
> language elements. The body of functions are "expressions", a particular R
> class.
>
> Here's another failed attempt:
>> body(B1) <- "{2*dnorm(T1(t),mean=32.5,sd=7)}"
>> B1
> function (T1, t)
> "{2*dnorm(T1(t),mean=32.5,sd=7)}"
>
> I knew that the quotes around the expression were NOT going to work. After
> successfully creating a function in the manner illustrated below I realized
> that you had not indicated what T1 was (and it appears to be a function), so
> it couldn't be tested. So I made a slightly simplified version:
>
>> B1<-function(t) (parms["B1"])   # starting with something like where you
>> are ...
>> body(B1) <- expression({2*dnorm(t, mean=32.5, sd=7)})
>> B1(32.5)
> [1] 0.1139835
>
> This might be a more clean method if you were starting all over:
>
>> B1 <- function(T1,t) { }
>> body(B1) <- expression({2*dnorm(T1(t), mean=32.5, sd=7)})
>> B1
> function (T1, t)
> {
>    2 * dnorm(T1(t), mean = 32.5, sd = 7)
> }
>>
>
>>
>>
>> Is there any way to do this?
>>
>> Thank you for your assistance and patience,
>> yours sincerely,
>>
>> Aimee Jones
>>
>> ______________________________________________
>> R-help at r-project.org 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.
>
> David Winsemius, MD
> West Hartford, CT
>
> ______________________________________________
> R-help at r-project.org 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.
>