R help - Sep 2010 - standardize columns selectively within a dataframe

Dear all,

I have a dataframe:   
df<-dataframe(a=c(1,2,3),b=c(4,5,6),c=c(7,8,9),d=c(10,11,12))

I want to obtain a new dataframe with columns a and b being standardized
((x-mean(x))/sd(x)); the other two columns (c,d) I want to leave
unchanged. What is the best way to achieve this? I have been trying to
use subscripts but did not succeed so far. 

Any tips?

Many thanks,
Olga

On Sep 1, 2010, at 10:35 AM, Olga Lyashevska wrote:
> Dear all,
>
> I have a dataframe:
> df<-dataframe(a=c(1,2,3),b=c(4,5,6),c=c(7,8,9),d=c(10,11,12))
>
> I want to obtain a new dataframe with columns a and b being  
> standardized
> ((x-mean(x))/sd(x)); the other two columns (c,d) I want to leave
> unchanged. What is the best way to achieve this? I have been trying to
> use subscripts but did not succeed so far.
 > df[ , 1:2] <- scale(df[ , 1:2])
 > df
    a  b c  d
1 -1 -1 7 10
2  0  0 8 11
3  1  1 9 12


-- 

David Winsemius, MD
West Hartford, CT

If you want to scale within columns, you could try

  cbind( scale(df[,1:2]), df[ ,-c(1:2)] )
     a  b c  d
  1 -1 -1 7 10
  2  0  0 8 11
  3  1  1 9 12

and it is data.frame() btw.


On 01/09/2010 15:35, Olga Lyashevska wrote:
> Dear all,
>
> I have a dataframe:
> df<-dataframe(a=c(1,2,3),b=c(4,5,6),c=c(7,8,9),d=c(10,11,12))
>
> I want to obtain a new dataframe with columns a and b being standardized
> ((x-mean(x))/sd(x)); the other two columns (c,d) I want to leave
> unchanged. What is the best way to achieve this? I have been trying to
> use subscripts but did not succeed so far.
>
> Any tips?
>
> Many thanks,
> Olga
>
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> and provide commented, minimal, self-contained, reproducible code.

Thanks! It is exactly what I was looking for!

Cheers
Olga