[R] string evaluation

[Wensui Liu]

Thank you so much, David. Your solution exactly suits my need.

formula() seems the key.

appreciate your help!

On Sat, Mar 12, 2011 at 10:22 AM, David Winsemius
<dwinsemius at comcast.net> wrote:
>
> On Mar 12, 2011, at 10:10 AM, Wensui Liu wrote:
>
>> Good morning, dear listers
>>
>> I am wondering how to do string evaluation such that
>>
>> model <- glm(Y ~ [STRING], data = mydata) where STRING <- "x1 + x2 + x3"
>>
>> It is very doable in other language such as SAS.
>
> Also "very doable" in R. You need to understand that R is a bit more
> structured than SAS, which is really just a macro-processor at least by
> heritage. Formulas are a language class in R and not just character vectors,
>  so you need to construct them outside the regression functions.
>
> STRING <- "x1 + x2 + x3"
> form <- formula(paste("Y ~ ", STRING) )
>  form
> # Y ~ x1 + x2 + x3
>  class(form)
> #[1] "formula"
>
>  model <- glm(form, data = mydata)
>
> --
> David Winsemius, MD
> West Hartford, CT
>
>



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WenSui Liu
Credit Risk Manager, 53 Bancorp
wensui.liu at 53.com
513-295-4370
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