R help - Jul 2011 - Utility function to apply a scale object on another data frame

Hi Everyone,

I would like to scale a data frame and then using the same scaling
parameters scale on another data frame. This will be helpful in scaling the
test dataset based on train dataset's scaling parameters. I couldn't
find
any utility functions that do this. Any suggestions on how to approach this
problem?

x = data.frame(a=1:10,b=11:20)
y = data.frame(a=2:11,b=12:21)
s <- scale(x)
###
### would like scale 'y' using the parameters contained in 's'

Thanks,
-e

	[[alternative HTML version deleted]]

On Jul 16, 2011, at 4:08 AM, E- Cognium wrote:
> Hi Everyone,
>
> I would like to scale a data frame and then using the same scaling
> parameters scale on another data frame. This will be helpful in  
> scaling the
> test dataset based on train dataset's scaling parameters. I
couldn't
> find
> any utility functions that do this. Any suggestions on how to  
> approach this
> problem?
>
> x = data.frame(a=1:10,b=11:20)
> y = data.frame(a=2:11,b=12:21)
> s <- scale(x)
> ###
> ### would like scale 'y' using the parameters contained in
's'
Just look at s and consult the obvious help page...
?attr

attr(s,"scaled:center")
attr(s,"scaled:scale")

-- 
David Winsemius, MD
West Hartford, CT

Hi "e",

Here is a simple function to use the attributes from one scaled object
to scale another.


x = data.frame(a=1:10,b=11:20)
y = data.frame(a=2:11,b=12:21)
s <- scale(x)

## function to scale x using attributes from trained
scale2 <- function(x, trained) {
  x <- as.matrix(x)
  x <- sweep(x, 2L, attr(trained, "scaled:center"), FUN =
"-")
  x <- sweep(x, 2L, attr(trained, "scaled:scale"), FUN =
"/")
  attr(x, "scaled:center") <- attr(trained,
"scaled:center")
  attr(x, "scaled:scale") <- attr(trained,
"scaled:scale")
  return(x)
}

## scale y from s
scale2(y, s)

HTH,

Josh

On Sat, Jul 16, 2011 at 1:08 AM, E- Cognium <ecognium at gmail.com>
wrote:
> Hi Everyone,
>
> I would like to scale a data frame and then using the same scaling
> parameters scale on another data frame. This will be helpful in scaling the
> test dataset based on train dataset's scaling parameters. I
couldn't find
> any utility functions that do this. Any suggestions on how to approach this
> problem?
>
> x = data.frame(a=1:10,b=11:20)
> y = data.frame(a=2:11,b=12:21)
> s <- scale(x)
> ###
> ### would like scale 'y' using the parameters contained in
's'
>
> Thanks,
> -e
>
> ? ? ? ?[[alternative HTML version deleted]]
>
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>


-- 
Joshua Wiley
Ph.D. Student, Health Psychology
University of California, Los Angeles
https://joshuawiley.com/