[R] Problem with col

[Sarah Goslee]

On Mon, Apr 20, 2015 at 12:56 PM, Sonia Amin <soniaamin5 at gmail.com> wrote:
> Sorry Sarah  for my basic question: what does "a column was read as factor"
> mean?

A factor is one of the basic types of data in R, and in statistics
generally, eg M/F or red/white/blue - a predetermined set of
categories that may or may not have an order.

More relevantly, if there's something wrong in your data, a stray
letter or quote mark for instance, that column is no longer numeric,
and R will read it as a factor by default, otherwise as character.

str(data)

which is NOT the same as just typing data, will show you the classes
of your columns, among other things.

> When I type data , I obtain all the numeric values and the headears  I added
> (Consommation,Cylindre,Puissance,Poids)

If you just look at data directly, you'll see what look like numbers,
perhaps, but according to R one or more columns are not actually
numbers. That's why you need str(data).

Your problem looks like a lack of basic understanding of how R works.
Here are a couple of sources that might help you get started:
http://www.burns-stat.com/documents/tutorials/impatient-r/
http://cyclismo.org/tutorial/R/


For more help, you should provide at least the output of str(data) to
the list, and ideally a reproducible example. Here are some
suggestions for creating a good reproducible example:
http://stackoverflow.com/questions/5963269/how-to-make-a-great-r-reproducible-example

Sarah

> Thanks
>
>
>
> 2015-04-20 18:40 GMT+02:00 Sarah Goslee <sarah.goslee at gmail.com>:
>>
>> What is the problem? One or more of your columns was read as factor, as
>>
>> str(data)
>>
>> would show you. To avoid this, you can add stringsAsFactors=FALSE to
>> the read.table command, but if you expect your data to be entirely
>> numeric then there's something wrong with it that you need to hunt
>> down.
>>
>> Sarah
>>
>> On Mon, Apr 20, 2015 at 12:33 PM, Sonia Amin <soniaamin5 at gmail.com> wrote:
>> > Dear All,
>> >
>> > I have written the following lines:
>> >
>> >
>> > data<-read.table("C:\\Users\\intel\\Documents\\SIIID\\datamultiplereg.txt",header
>> > = FALSE, sep = "")
>> >  colnames(data)<-c("Consommation","Cylindre","Puissance","Poids")
>> >  result.model1<-lm(Consommation~Cylindre+Puissance+Poids, data=data)
>> > summary(result.model1)
>> >
>> > I obtained the following message:
>> >
>> >
>> > Call:
>> > lm(formula = Consommation ~ Cylindre + Puissance + Poids, data = data)
>> >
>> > Residuals:
>> > Error in quantile.default(resid) : factors are not allowed
>> > In addition: warning message:
>> > In Ops.factor(r, 2) :
>> >   ‘^’ This is not relevant for factors
>> >
>> >
>> > Where is the problem?
>> > Thank you in advance
>> >
>> --
>> Sarah Goslee
>> http://www.functionaldiversity.org
>
>