Thank you both so much for your help!  I ended up using
bquote(expression(...)), and it's working perfectly!

On Sat, May 5, 2012 at 1:05 PM, David Winsemius <dwinsemius@comcast.net>wrote:

>
> On May 5, 2012, at 2:42 PM, Josh Browning wrote:
>
>  Hello useRs!
>>
>> So, I have a random question.  I'm trying to build a character string,
>> then
>> evaluate it.
>>
>
> Actually you are trying to build a language object , a call or an
> expression. You might have gotten further with:
>
> do.call(ksvm, list(  ... named arguments ...)
>
>
>   I think an example would be the easiest way to explain:
>>
>>
>>   kern.vec = c("rbfdot","polydot")
>>   for( j in 1:length( kern.vec ) )
>>   {
>>     formula    = paste("ksvm( ind ~ . ,
>> data=d.temp[,c(ind_col,dep_**cols)], kernel =",kern.vec[j],",
>> prob.model=T )")
>>     svm    = eval( parse( text=formula ) )
>>    ...
>>   }
>>
>>
>> The problem I always seem to have is that in the formula, I need to have
>> quotes around "rbfdot" (for example).  But, when I paste the expression
>> together, it removes the quotes.  Is there a better way to do this (or at
>> least a way around this problem)?  My method seems a bit kludgy :)
>>
>
> Perhaps looking at either:
>
> ?substitute
> ?bquote
>
>
> kern.vec = c("rbfdot","polydot")
>   for( j in 1:length( kern.vec ) )
>   {
>     formula    = bquote(expression( ksvm( ind ~ . ,
> data=d.temp[,c(ind_col,dep_**cols)], kernel =.(kern.vec[j] ) ,
> prob.model=T ) ))
>     print(formula)
>   }
>
> expression(ksvm(ind ~ ., data = d.temp[, c(ind_col, dep_cols)],
>    kernel = "rbfdot", prob.model = T))
> expression(ksvm(ind ~ ., data = d.temp[, c(ind_col, dep_cols)],
>    kernel = "polydot", prob.model = T))
>
> Notice that the values for kern.vec are 'character' which is what you
> passed them (and what you seem to be requesting. If you wanted the values
> of those named objects you might try get(<name>). (I'm not a user of
> whatever package has `ksvm` in it, so I'm not aware of whether 'rbfdot' is
> supposed to be a character value as a parameter or if those are named
> objects, and I'm not running out to identify the package and then to locate
> a working example to test the eval-result. Those are details you should
> have provided.)
>
>>
>>
>
> --
>
> David Winsemius, MD
> West Hartford, CT
>
>

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