... and anyone can comment the code
* -irecode()- maps to integers 0, 1, ...
Nick
n.j.cox@durham.ac.uk
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu
> [mailto:owner-statalist@hsphsun2.harvard.edu]On Behalf Of Jeph Herrin
> Sent: 20 August 2006 19:42
> To: statalist@hsphsun2.harvard.edu
> Subject: Re: st: RE: < and > operand in recode
>
>
> Agree about the start integer being non-intuitive, and I suppose
> making it an argument to -irecode- would just mean looking it up
> that much more often (to recall which argument it was...).
>
>
>
> Nick Cox wrote:
> > This is indeed a further possibility.
> >
> > -irecode()- is a well-defined Stata function and
> > this gives a concise one-line solution. And
> > the definition is there in the help.
> >
> > I'll declare prejudices, however. -irecode()-
> > is a function I rarely use, so I would
> > have to look at the help to check the
> > definitions. (The results run 0 up;
> > an equally defensible rule is that
> > results run 1 up, and I would have
> > to look up to see which was Stata's
> > choice.) Also, this is to my mind
> > less transparent than -cond()-.
> >
> > But these prejudices will not
> > be compelling for all readers,
> > and are mentioned mostly to
> > explain why I didn't think of
> > that.
> >
> > Nick
> > n.j.cox@durham.ac.uk
> >
> > Jeph Herrin
> >
> >> What about:
> >>
> >> . gen newvar = irecode(var,1,2,5,10,.)+1
> >>
> >> ?
> >>
> >> Nick Cox wrote:
> >>> Terminology appears to be a small problem here.
> >>>
> >>> I understand = to indicate equality and >, >=, < or <=
> >>> to indicate inequality. Your contradictory usage
> >>> is rather surprising.
> >>>
> >>> That aside, the key point is that -recode- is announced
> >>> as for recoding categorical variables, meaning
> >>> in practice categorical variables coded as
> >>> integers.
> >>>
> >>> -recode- does allow many-to-one mappings, but it
> >>> really is not a good idea to use it for re-coding
> >>> a continuous variable. Even though your work-around
> >>> apparently worked for you, it is no more than
> >>> a work-around. Also, there are plenty of possible
> >>> values between 0 and 0.0001, etc., and testing
> >>> for equality and inequality with a decimal fraction
> >>> is usually problematic.
> >>>
> >>> Now Stata as such doesn't really have any idea
> >>> of what a categorical variable is, and thus does
> >>> not declare your use to be an error, although
> >>> there are several good arguments for strictness
> >>> in such matters (or at least for a -force- option
> >>> which shows that you realise exactly what
> >>> you are doing).
> >>>
> >>> For your coding a perfectly respectable
> >>> approach is
> >>>
> >>> gen newvar = 1 if var <= 1
> >>> replace newvar = 2 if var <= 2 & missing(newvar)
> >>> replace newvar = 3 if var <= 5 & missing(newvar)
> >>> replace newvar = 4 if var <= 10 & missing(newvar)
> >>> replace newvar = 5 if var < . & missing(newvar)
> >>> replace newvar = . if var == .
> >>>
> >>> That may look long-winded, but it is perfectly
> >>> explicit and easy to understand.
> >>>
> >>> Another perfectly respectable approach is
> >>> make use of -inrange(,)-:
> >>>
> >>> gen newvar = 1 if inrange(var,.,1)
> >>> replace newvar = 2 if inrange(var,1,2) & missing(newvar)
> >>> replace newvar = 3 if inrange(var,2,5) & missing(newvar)
> >>> replace newvar = 4 if inrange(var,5,10) & missing(newvar)
> >>> replace newvar = 5 if inrange(var,10,.) & missing(newvar)
> >>> replace newvar = . if var == .
> >>>
> >>> although with -inrange()- it is not so transparent
> >>> what happens in the case of equality with either
> >>> argument. See the help for -inrange()-.
> >>>
> >>> Yet another perfectably respectable approach is to
> >>> make use of -cond()-.
> >>>
> >>> gen newvar = cond(var <= 1, 1,
> >>> cond(var <= 2, 2,
> >>> cond(var <= 5, 3,
> >>> cond(var <= 10, 4,
> >>> cond(var < ., 5, .)))))
> >>>
> >>> That is all one command. Careful layout and use
> >>> of a good text editor to check balanced parentheses
> >>> are recommended.
> >>>
> >>> Personally, for your example problem, I like -cond()- best.
> >>>
> >>> For a discursive tutorial see
> >>>
> >>> SJ-5-3 pr0016 . . Depending on conditions: a tutorial on
> >> the cond() function
> >>> . . . . . . . . . . . . . . . . . . . . . . . D.
> >> Kantor and N. J. Cox
> >>> Q3/05 SJ 5(3):413--420
> >> (no commands)
> >>> tutorial on the cond() function
> >>>
> >>>
> >>> Nick
> >>> n.j.cox@durham.ac.uk
> >>>
> >>> b. water
> >>>
> >>>> Stata 8.2,
> >>>>
> >>>> i wanted to recode a variable, which consisted of continuous
> >>>> number, something to the effect of:
> >>>>
> >>>> <=1 coded 1 (<= i.e. meaning less than or equal to)
> >>>>> 1 to <=2 coded 2
> >>>>> 2 to <= 5 coded 3
> >>>>> 5 to <=10 coded 4
> >>>>> 10 coded 5
> >>>> when i tried to use the equality operands (i.e. < or > in my
> >>>> recode commands, it gives an error message 'unknown el <2 in
> >>>> rule') so after consulting my manual on [R] recode, i managed
> >>>> by recoding:
> >>>>
> >>>> 0.0001/1 = 1
> >>>> 1.0001/2 = 2
> >>>> .
> >>>> .
> >>>> 10/1000 = 5
> >>>> etc
> >>>>
> >>>> being careful to make sure that the parameters included all
> >>>> the values.
> >>>>
> >>>> i would appreciate if someone could confirm that equality
> >>>> sign cannot be used in recode. would appreciate it too if
> >>>> anyone can point out an alternative/better way to accomplish
> >>>> the recode.
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