On Thu, Apr 16, 2009 at 5:58 PM, Kavitha Venkatesan <
kavitha.venkatesan@gmail.com> wrote:

> I would like to know how to evaluate a character string as a variable name
> in R. Specifically, I need to "compute" the variable name in the phenoData
> slot of an ExpressionSet object.
>
> > varLabels(sample.ExpressionSet)
> [1] "sex"   "type"  "score"
>
> Now I need to retrieve the factors sample.ExpressionSet$sex,
> sample.ExpressionSet$type and sample.ExpressionSet$score in turn.
> Furthermore, I need to be able to generalize my code so that I can retrieve
> this factor for any phenodata variable in any given ExpressionSet object.
>
> Clearly I cannot do something like
>
> for (i in c(1:length(varLabels(sample.ExpressionSet)))
> {
> class_label <- varLabels(sample.ExpresionSet)[i]
> class_label_factor <-  sample.ExpressionSet$class_label
> }
>
> Here class_label is interpreted as a character string by R, but I need for
> it to be evaluated as a variable name. Seems straightforward, but I
> couldn't
> figure it out...How can I do this? Thanks in advance for any help!
>

If i is your class label:

pData(sample.ExpressionSet)[,i]

does that do what you need?

Sean

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