R help - Jun 2008 - "& not meaningful for factors"

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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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 <
nana_kwadwo_derkyi@yahoo.com> 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
>
>
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> 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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