[R] a symbolic derivative question, please

[Duncan Murdoch]

On 09/01/2015 2:04 PM, Erin Hodgess wrote:
> One more thing, please:  (just like Columbo)
> 
> Is there a work-around for this, please?

I did some work with John Nash a few months ago that gave symbolic
derivative code that was a bit more flexible than the built-in code.
It's on R-forge in the nls14 package.

With that package, you get the same error as in base, but you can do

newDeriv(`[`(x,y), stop("no derivative when indexing"))

and then fnDeriv() (the nls14 replacement for deriv()) works on your
example.

Duncan Murdoch

> 
> Thanks again,
> Erin
> 
> 
> On Fri, Jan 9, 2015 at 1:09 PM, Richard M. Heiberger <rmh at temple.edu> wrote:
> 
>> `[` is a function.  So the deriv program is seeing
>>
>> `[`(y,3)*r1 + r2
>>
>>> letters[5]
>> [1] "e"
>>> `[`(letters, 5)
>> [1] "e"
>>
>> On Fri, Jan 9, 2015 at 12:31 PM, Erin Hodgess <erinm.hodgess at gmail.com>
>> wrote:
>>> Hello!
>>>
>>> I have the following:
>>>
>>> zzz <- expression(y[3]*r1 + r2)
>>> deriv(zzz,c("r1","r2"))
>>> Error in deriv.default(zzz,c("r1","r2")) :
>>>    Function '`[`' is not in the derivatives table
>>>
>>> What am I missing, please?  Since y is not one of the variables that is
>>> being "acted upon", why is the [] an issue, please?
>>>
>>> Thank you for any help!
>>>
>>> Sincerely,
>>> Erin
>>>
>>>
>>> --
>>> Erin Hodgess
>>> Associate Professor
>>> Department of Mathematical and Statistics
>>> University of Houston - Downtown
>>> mailto: erinm.hodgess at gmail.com
>>>
>>>         [[alternative HTML version deleted]]
>>>
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> 
> 
>