What exactly are you trying to do? In the first case you are making a
logical comparison and that is legal for "&". In the second you are trying
to do a logical operation ("&") between two factors and that operation is
not defined. This is what the error message is saying.
Also you first attempt is probably missing a comma:
node1 <- data.trt[data.trt$stage=="1B" & data.trt$diameter=="=< 4", ]
On Wed, Jun 4, 2008 at 8:10 AM, Philip Twumasi-Ankrah <
[EMAIL PROTECTED]> wrote:
> I am trying to define groupings from levels of factor variables and this
> the warning message that R give
>
> "& not meaningful for factors".
>
> The nature of my task is this. I have a variable stage which has the levels
> (1B, 2A, 2B) - these are the AJCC TNM stages of cancer, and another variable
> diameter with factor levels ("=< 4", "4 - 6.5, > 6.5; limit values are
> exclusive).
>
> I am trying to define series of groupings based on these variables and
> others like them.
>
> My first attempts were;
>
> 1. node1 <- data.trt[data.trt$stage=="1B" & data.trt$diameter=="=< 4"]
> 2. data.trt$stage[data.trt$stage=="1B"]&
> data.trt$diameter[data.trt$diameter=="=< 4"]
>
> The second attempt was purely a fishing exercise.
>
> R gave me the waring message:
>
> Warning message:
> In Ops.factor(data.trt$stage[data.trt$stage == "1B"],
> data.trt$diameter[data.trt$diameter == :
> & not meaningful for factors
>
>
> My question is how do I get round this and by implication is there an
> alternative way of defining a logical operation applicable to factors.
>
> Thanks already for the help.
>
> Philip
>
>
> A Smile costs Nothing
>
> But Rewards Everything
>
> Happiness is not perfected until it is shared
> -Jane Porter
>
>
>
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>
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> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>
--
Jim Holtman
Cincinnati, OH
+1 513 646 9390
What is the problem you are trying to solve?
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