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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