[R] Using optimize with array variables

[Charles C. Berry]

On Thu, 1 Oct 2009, Vik wrote:

> Thanks Charles, I have been able to change the function and to make it work.
> I have also gotten the same results using nlm().
>
> Now the question I have (and that google has not helped on) is which
> optimization functions can I use for solving for two distinct variables
> instead of only one? Thanks again.

Once again, the _posting guide_ rides to the rescue.

Following the advice there,

 	RSiteSearch("optimization",restric="functions")

would have answered your question.

:-)


>
> On Thu, Oct 1, 2009 at 1:06 PM, Charles C. Berry <cberry at tajo.ucsd.edu>wrote:
>
>> On Thu, 1 Oct 2009, Vik wrote:
>>
>>  Hello,
>>>
>>> I am trying to figure out how to use optimize() with array variables
>>> as inputs. I have a for loop in the function definition:
>>>
>>> SS <- function(int,slo,x,y){
>>> for(i in 1:length(x)) ((int+slo*x[i])-y[i])^2->squares[i]
>>> sum(squares)->>sum_squares
>>> output_txt = c ("The sum of squares is", sum_squares)
>>> print(output_txt, quote=FALSE)}
>>>
>>>
>>
>> Try running your code in a clean session. There is an error (and not the
>> one you quote below).
>>
>>
>> After you get rid of that error, try
>>
>>        val <- SS ( 0.1, 1, 1, 1 )
>>
>> then
>>
>>        print( val )
>>
>> The difficulty optimize is having should be apparent.
>>
>> In spite of the pressure you are under, you will need to slow down, write
>> readable code, and take the time to learn about writing functions in R
>> before you can hope to get anywhere with a problem like this.
>>
>> Read the posting guide. For a problem like this one, the 'Some' mentioned
>> below includes many of the people on this list who can provide useful,
>> knowledgeable answers:
>>
>>        Some consider it good manners to include a concise signature
>>        specifying affiliation
>>
>>
>> HTH,
>>
>> Chuck
>>
>>
>> p.s. do not use '<<-' or '->>' until you really, really know what it does
>> (which means you understand 'scoping')!
>>
>>  Even assuming I make x and y single-integer variables, for example:
>>>
>>> optimize(SS, c(0,1), tol = 0.0001, x=1, y=1, slo=1)
>>>
>>> I get the error:
>>>
>>> Error in optimize(SS, c(0, 1), tol = 1e-04, x = 1, y = 1, slo = 1) :
>>>  invalid function value in 'optimize'
>>>
>>> Not sure what that means. This also happens when x and y are defined
>>> as arrays. Does optimize require me to input values for all variables
>>> that are not being optimized (i.e. for n-1 of the inputs)? Why am I
>>> getting an error.
>>>
>>> I am new to R and under pressure to get some calculations done for my
>>> work. I'd appreciate an answer to the specific question - and I fully
>>> understand that I need to read up on R basics in more depth, which I
>>> am doing as best I can while trying to get this work done. Thanks!
>>>
>>> ______________________________________________
>>> 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.
>>>
>>>
>> Charles C. Berry                            (858) 534-2098
>>                                            Dept of Family/Preventive
>> Medicine
>> E mailto:cberry at tajo.ucsd.edu               UC San Diego
>> http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901
>>
>>
>>
>
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
> 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.
>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901