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.

On Thu, Oct 1, 2009 at 1:06 PM, Charles C. Berry <cberry@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@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@tajo.ucsd.edu               UC San Diego
> http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901
>
>
>

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