[R] Factor levels in training set

[PIKAL Petr]

Hi Elahe

I get slightly different error when using scale to nonnumeric data so I am not sure if you use the scale function from base package.

> scale(raman[1:20,])
Error in colMeans(x, na.rm = TRUE) : 'x' must be numeric

Anyway, how do you expect scaling shall be done when you have nonumeric variable. What shall be the output of

scale(iris$Species)

The only workaround is either to scale only numeric variables from your data and add nonnumeric in folowing step or to change all factor variable to numeric before scaling (which I would not recommend).

If your data are supposed to be numeric you can check if they really are by

str(df)

Cheers
Petr

> -----Original Message-----
> From: R-help [mailto:r-help-bounces at r-project.org] On Behalf Of ch.elahe
> via R-help
> Sent: Tuesday, June 14, 2016 5:29 PM
> To: R-help Mailing List <r-help at r-project.org>
> Subject: [R] Factor levels in training set
>
>
>  Hi all,
> I want to use Supervised Self organizing Maps from Kohonen package for my
> data. I need to divide my df into training set and test set, but a part of my df
> contains column with factor levels and I don't know how to bring them into
> my training set. Currently I use the following command for my training set:
>
>     dt=sort(sample(nrow(df),nrow(df)*.7))
>     training=m[dt,]
> till here I get no error but in the next step which I need to bring my training
> set in a matrix I face this error:
>
>     scale(df[training,])
> error: 'x' should be numeric
> Does anyone know how should I include column with factor levels in my df so
> that I don't get this error?
> Thanks for any help,
> Elahe
>
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