# Re: [R] "& not meaningful for factors

Date: Wed, 04 Jun 2008 05:47:05 -0700 (PDT)

It works. Thanks Jim. I guess this will be a "lots of coffee" morning kinda day.

jim holtman <jholtman_at_gmail.com> wrote: 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_at_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.

Philip

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