R help - Mar 2012 - Remove quotes from a string to use in a variable call

Hi,

I have a string that I want to use in a variable call.  How can I remove the
quotes and/or the string properties of the string to use it in a variable
call?

Here's an example:

library(lme)
fm2 <- lme(distance ~ age, data = Orthodont, random = ~ 1)
summary(fm2)

I want to update the above regression to include new predictors according to
what is in a string:

predictors <- "age + Sex"
update(fm2,fixed=distance ~ age + Sex) #this works
update(fm2,fixed=distance ~ noquote(predictors)) #this doesn't work

Any help would be greatly appreciated.  Thanks!

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Hello,



dadrivr wrote
> 
> Hi,
> 
> I have a string that I want to use in a variable call.  How can I remove
> the quotes and/or the string properties of the string to use it in a
> variable call?
> 
> Here's an example:
> 
> library(nlme)
> fm2 <- lme(distance ~ age, data = Orthodont, random = ~ 1)
> summary(fm2)
> 
> I want to update the above regression to include new predictors according
> to what is in a string:
> 
> predictors <- "age + Sex"
> update(fm2,fixed=distance ~ age + Sex) #this works
> update(fm2,fixed=distance ~ noquote(predictors)) #this doesn't work
> 
> Any help would be greatly appreciated.  Thanks!
> 
Try

response <- "distance"
predictors <- "age + Sex"
fmla.text <- paste(response, predictors, sep="~")

update(fm2,fixed=as.formula(fmla.text))

Hope this helps,

Rui Barradas



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