R help - Nov 2012 - Scaling values 0-255 -> -1 , 1 - how can this be done?

I have a dataframe in which I have values 0-255, I wish to transpose them such
that:

if value  > 127.5 value = 1
if value < 127.5 value = -1

I did something similar using the "binarize" function of the biclust
package, this transforms my dataframe to 0 and 1 values, but I wish
to use -1 and 1 and looking for a way in R to do this.

Brian

On Nov 21, 2012, at 9:32 AM, Brian Feeny <bfeeny at me.com> wrote:
> 
> I have a dataframe in which I have values 0-255, I wish to transpose them
such that:
> 
> if value  > 127.5 value = 1
> if value < 127.5 value = -1
> 
> I did something similar using the "binarize" function of the
biclust package, this transforms my dataframe to 0 and 1 values, but I wish
> to use -1 and 1 and looking for a way in R to do this.
> 
> Brian
See ?ifelse

  ifelse(value > 127.5, 1, -1)

You might want to think about what happens when value == 127.5 ...

Regards,

Marc Schwartz

fakedata <- data.frame(matrix(sample(1:255, 50, replace=TRUE), ncol=5))
ifelse(fakedata > 127.5, 1, -1)

Sarah

On Wed, Nov 21, 2012 at 10:32 AM, Brian Feeny <bfeeny at me.com>
wrote:
>
> I have a dataframe in which I have values 0-255, I wish to transpose them
such that:
>
> if value  > 127.5 value = 1
> if value < 127.5 value = -1
>
> I did something similar using the "binarize" function of the
biclust package, this transforms my dataframe to 0 and 1 values, but I wish
> to use -1 and 1 and looking for a way in R to do this.
>
> Brian
>

--
Sarah Goslee
http://www.functionaldiversity.org

x <- as.data.frame( matrix( 0:255, nrow = 16 ) )
ifelse( x > 127.5, 1, -1 )

Is that what you want?

Rgds,
Rainer


On Wednesday 21 November 2012 10:32:49 Brian Feeny
wrote:
> 
> I have a dataframe in which I have values 0-255, I wish to transpose them
such that:
> 
> if value  > 127.5 value = 1
> if value < 127.5 value = -1
> 
> I did something similar using the "binarize" function of the
biclust package, this transforms my dataframe to 0 and 1 values, but I wish
> to use -1 and 1 and looking for a way in R to do this.
> 
> Brian
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.

HI,
You could also use:
set.seed(5)
?x1<-data.frame(matrix(sample(0:255,80,replace=TRUE),ncol=10))
library(car)
?do.call(cbind,lapply(x1,function(x)
x<-recode(x,"0:127.5=-1;127.6:255=1")))
#???? X1 X2 X3 X4 X5 X6 X7 X8 X9 X10
#[1,] -1? 1 -1 -1 -1? 1? 1 -1? 1? -1
#[2,]? 1 -1? 1 -1 -1 -1? 1 -1? 1?? 1
#[3,]? 1 -1? 1 -1 -1? 1 -1 -1? 1? -1
#[4,] -1 -1? 1? 1 -1? 1? 1 -1 -1?? 1
#[5,] -1 -1? 1 -1? 1? 1? 1? 1? 1? -1
#[6,]? 1? 1? 1? 1? 1? 1? 1 -1? 1?? 1
#[7,]? 1 -1 -1 -1 -1? 1? 1? 1? 1? -1
#[8,]? 1 -1 -1 -1 -1 -1 -1? 1? 1? -1
A.K.




----- Original Message -----
From: Brian Feeny <bfeeny at me.com>
To: r-help at r-project.org
Cc: 
Sent: Wednesday, November 21, 2012 10:32 AM
Subject: [R] Scaling values 0-255 -> -1 , 1 - how can this be done?


I have a dataframe in which I have values 0-255, I wish to transpose them such
that:

if value? > 127.5 value = 1
if value < 127.5 value = -1

I did something similar using the "binarize" function of the biclust
package, this transforms my dataframe to 0 and 1 values, but I wish
to use -1 and 1 and looking for a way in R to do this.

Brian

______________________________________________
R-help at r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-help
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

> Subject: Re: [R] Scaling values 0-255 -> -1 , 1 - how can 
> this be done?
#Also by taking advantage of numerical interpretation of booleans:
x<- sample(255)  #toy data

2*( x > 127.5 )  - 1

#S Ellison

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On Nov 21, 2012, at 7:32 AM, Brian Feeny wrote:
>
> I have a dataframe in which I have values 0-255, I wish to transpose  
> them such that:
>
> if value  > 127.5 value = 1
> if value < 127.5 value = -1
>
c(-1, 1)[ 1+(value > 127.5) ]

I suspect most will find this less intuitive than `ifelse`, but I find  
it useful when picking colors or other values from a vector,  
expecially when the argument is built with findInterval, e.g.

c(-1, 1)[ findInterval(value, c(0, 127.5, 255) ) ] Which generalizes  
much more compactly to multiple intervals than does ifelse.

> I did something similar using the "binarize" function of the
biclust
> package, this transforms my dataframe to 0 and 1 values, but I wish
> to use -1 and 1 and looking for a way in R to do this.
-- 

David Winsemius, MD
Alameda, CA, USA