R help - Sep 2007 - How to Standardise the x/y coordinates to the unit square?

Dear Rusers, I want to standardise the values of x/y coordinates to the unit
square, i.e. make the x-values all lie within [0,1] and all the y-values lie
within [0,1] in the bottom example.  I had thought to use scale() function to do
it, but it seems that it's used to standardise a variable and the scaled
value was not within [0,1]. OR, i can divide x/y-values by their maximum value
to get it.  I'm not sure about it.#Example data data <- matrix(1:10,
nc=2)
data<-as.data.frame(data)
names(data)<-c('x','y')> data
  x  y
1 1  6
2 2  7
3 3  8
4 4  9
5 5 10  I'd appreciate your help. 
--
Kind Regards,
John Chang
	[[alternative HTML version deleted]]

??? wrote:
> Dear Rusers, I want to standardise the values of x/y coordinates to the
unit square, i.e. make the x-values all lie within [0,1] and all the y-values
lie within [0,1] in the bottom example.  I had thought to use scale() function
to do it, but it seems that it's used to standardise a variable and the
scaled value was not within [0,1]. OR, i can divide x/y-values by their maximum
value to get it.  I'm not sure about it.#Example data
> data <- matrix(1:10, nc=2)
> data<-as.data.frame(data)
> names(data)<-c('x','y')
> > data
>   x  y
> 1 1  6
> 2 2  7
> 3 3  8
> 4 4  9
> 5 5 10 
>  I'd appreciate your help.
(Beware line formatting in your emails)

You can actually use scale(), but it is hardly worth it and an abuse of
concepts. Just write a little function for the actual scaling and apply
it to each column.

st <- function(x)(x-min(x))/(max(x)-min(x))
data.frame(lapply(data,st))

Or,

d.min <- apply(data,2,min)
d.max <- apply(data,2,max)
sweep(sweep(data, 2, d.min, "-"), 2, d.max - d.min, "/")

or, same thing using scale()

scale(data, center=d.min, scale=d.max - d.min)
>  
> --
> Kind Regards,
> John Chang
> 	[[alternative HTML version deleted]]
>
> ______________________________________________
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> PLEASE do read the posting guide
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>   

-- 
   O__  ---- Peter Dalgaard             ?ster Farimagsgade 5, Entr.B
  c/ /'_ --- Dept. of Biostatistics     PO Box 2099, 1014 Cph. K
 (*) \(*) -- University of Copenhagen   Denmark          Ph:  (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)                  FAX: (+45) 35327907

??? wrote:
> Dear Rusers, I want to standardise the values of x/y coordinates to the
unit square, i.e. make the x-values all lie within [0,1] and all the y-values
lie within [0,1] in the bottom example.  I had thought to use scale() function
to do it, but it seems that it's used to standardise a variable and the
scaled value was not within [0,1]. OR, i can divide x/y-values by their maximum
value to get it.  I'm not sure about it.#Example data data <-
matrix(1:10, nc=2)
> data<-as.data.frame(data)
> names(data)<-c('x','y')> data
>   x  y
> 1 1  6
> 2 2  7
> 3 3  8
> 4 4  9
> 5 5 10  I'd appreciate your help. 
> --
Hi John,
You can do this with the "rescale" function in the plotrix package.

newx<-rescale(x,c(0,1))
newy<-rescale(y,c(0,1))

Jim