[R] cut and factor

[Achim Zeileis]

On Tue, 30 Mar 2004 00:06:39 +0400 (MSD) Oleg Bartunov wrote:

> Eric,
> 
> thanks for quick reply. at first look I thought it is what I need,
> but, unfortunately, it doesn't applied to original data - it
> creates new data with loosing original indexes ! I want to keep
> indexes of original data, but replace original data with $mids of
> corresponding$breaks.

Then you just don't say table() after using cut().
 
> So, if I have z = 1:10, t=hist(z,plot=F)
> > z
>  [1]  1  2  3  4  5  6  7  8  9 10
> > t$breaks
> [1]  0  2  4  6  8 10
> > t$mids
> [1] 1 3 5 7 9
> 
> I want z=c(1,1,3,3,5,5,7,7,9,9)

and you get it via

R> z <- 1:10
R> ht <- hist(z,plot=F)
R> z
 [1]  1  2  3  4  5  6  7  8  9 10
R> ht$breaks
[1]  0  2  4  6  8 10
R> ht$mids
[1] 1 3 5 7 9
R> z2 <- cut(z, ht$breaks, labels = ht$mids)
R> z2
 [1] 1 1 3 3 5 5 7 7 9 9
Levels: 1 3 5 7 9

or if you don't want to have a factor

R> as.numeric(as.character(z2))
 [1] 1 1 3 3 5 5 7 7 9 9

best,
Z

> 
> 	Oleg
> 
> On Mon, 29 Mar 2004, Erin Hodgess wrote:
> 
> > Hello Oleg!
> >
> > Do you mean something like this, please?
> > > z <- rnorm(15)
> > > z
> >  [1] -0.36888946  0.34271755 -0.47761843 -0.58402557  0.05393014 
> >  0.69234710
> > 2.04861420  1.41823938 -0.57638598  1.51090023
> > [11] -0.71616401  0.19227347 -0.19348506 -0.63082326 -0.64346621
> > > z1 <- hist(z,plot=F)
> > > z1$breaks
> > [1] -1.0 -0.5  0.0  0.5  1.0  1.5  2.0  2.5
> > > table(cut(z,z1$breaks))
> >
> > (-1,-0.5]  (-0.5,0]   (0,0.5]   (0.5,1]   (1,1.5]   (1.5,2]  
> > (2,2.5]
> >         5         3         3         1         1         1        
> >         1
> >
> > Hope this helps!
> > Sincerely,
> > Erin Hodgess
> > Associate Professor
> > Department of Computer and Mathematical Sciences
> > University of Houston - Downtown
> > mailto: hodgess at gator.uhd.edu
> >
> >
> >
> > From: Oleg Bartunov <oleg at sai.msu.su>
> >
> >
> > I have numeric vector z and I want to factorize it using z$breaks
> > which I got from histograms breaks. Is there an elegant way to do
> > this ? I, probably, could write a loop and check if z hits into some
> > interval and replace z with value of z$mids, but I suspect there is
> > more R-ish way.
> >
> > 	Regards,
> > 		Oleg
> > _____________________________________________________________
> > Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> > Sternberg Astronomical Institute, Moscow University (Russia)
> > Internet: oleg at sai.msu.su, http://www.sai.msu.su/~megera/
> > phone: +007(095)939-16-83, +007(095)939-23-83
> >
> 
> 	Regards,
> 		Oleg
> _____________________________________________________________
> Oleg Bartunov, sci.researcher, hostmaster of AstroNet,
> Sternberg Astronomical Institute, Moscow University (Russia)
> Internet: oleg at sai.msu.su, http://www.sai.msu.su/~megera/
> phone: +007(095)939-16-83, +007(095)939-23-83
> 
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