st: Re: RE: Re: RE: RE: Continous to categorical variable

["Sergiy Radyakin" <Radyakin@aoek.uni-hannover.de>]

All you need is to select your intervals to be smaller at the ends and wider 
in the middle.

The simpliest way to do this is:
1. Normalize your data -- subtract the min, divide by the range, you know 
the story -- your values should be [0;1]
2. Treat these values as probabilites p, and solve Fnorm(x)=p for x. In 
Stata use -invnorm-
3. Now you have remapped your values to a range about [-3;3]
4. Divide this range to the desired number of categories, e.g. 6: [-3;-2], 
[-2,-1], ....
5. Done

N.b. invnorm(0)=.
       invnorm(1)=.
So you will lose the max and the min points in your data. You can assign 
them manually to the respective categories.

Regards, Sergiy


----- Original Message ----- 
From: "Mentzakis, Emmanouil" <e.mentzakis@abdn.ac.uk>
To: <statalist@hsphsun2.harvard.edu>
Sent: Wednesday, February 21, 2007 6:33 PM
Subject: st: RE: Re: RE: RE: Continous to categorical variable



> Yes, something like that would be nice but note that my continous
> variable has 62,000 unique values so I cannot do them by hand.
>
> Thank you
> Manos
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Sergiy
> Radyakin
> Sent: 21 February 2007 17:16
> To: statalist@hsphsun2.harvard.edu
> Subject: st: Re: RE: RE: Continous to categorical variable
>
> Why would you want to do that?
>
> Would this be something you are looking for?
>
>
> ------------------------------------------
> input educ
> 1
> 2
> 3
> 4
> 5
> 6
> 7
> 8
> 9
> 10
> 11
> 12
> 13
> 14
> 15
> 16
> 17
> 18
> 19
> 20
> end
> hist educ,d
> recode educ (1=1) (2 3=2) (4 5 6=3) (7 8 9 10=4) (11 12 13 14=5) (15 16
> 17=6) (18 19=7) (20=8),gen(educ2)
> hist educ2,d
> ------------------------------------------
>
> Now if you do:
>
> scatter educ educ2
>
> you will realize that you need to place the cut off points at the
> quantiles of the normal distribution (transformed properly for your
> data)
>
>
>
> Sergiy
>
>
>
>
>
>
>
>
> ----- Original Message ----- 
> From: "Mentzakis, Emmanouil" <e.mentzakis@abdn.ac.uk>
> To: <statalist@hsphsun2.harvard.edu>
> Sent: Wednesday, February 21, 2007 6:03 PM
> Subject: st: RE: RE: Continous to categorical variable
>
>
>
> > Maybe I should describe a little bit better.
> >
> > I do not want the variable to "become more like a normal
> distribution".
> > What I would like is the categories created to be such that the tails
> > contain less individuals, with an increase in the numbers as we get
> > closer to the middle category.
> >
> > Thanks
> > Manos
> >
> > -----Original Message-----
> > From: owner-statalist@hsphsun2.harvard.edu
> > [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Maarten
> Buis
> > Sent: 21 February 2007 16:48
> > To: statalist@hsphsun2.harvard.edu
> > Subject: st: RE: Continous to categorical variable
> >
> > --- Mentzakis, Emmanouil wrote:
> > > I have a continous variable (i.e. income) and I would like to
> > > transform it into a categorical one (e.g 5 categories/levels or
> more).
> > > I would like to ask if there is any way that I can ask stata to
> create
> > > this variable deciding the appropriate cut-off points automatically
> so
> > > that the categories follow aproximately a normal distrubution or they
> > > are of equal size.
> > For the latter have a look at -help egen- and look at the cut
> function.
> > For the former: how would you expect a variable to become more like a
> > normal distribution by making it coarser?
> >
> > Hope this helps,
> > Maarten
> >
> > -----------------------------------------
> > Maarten L. Buis
> > Department of Social Research Methodology Vrije Universiteit Amsterdam
> > Boelelaan 1081
> > 1081 HV Amsterdam
> > The Netherlands
> >
> > visiting address:
> > Buitenveldertselaan 3 (Metropolitan), room Z434
> >
> > +31 20 5986715
> >
> > http://home.fsw.vu.nl/m.buis/
> > -----------------------------------------
> >
> >
> >
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