Dear Soko,
distance = lalonde$ps should do it.
Cheers,
Kosuke
-----------------------------------------------------
Kosuke Imai Office: Corwin Hall 041
Assistant Professor Phone: 609-258-6601
Department of Politics eFax: 973-556-1929
Princeton University Email: kimai(a)Princeton.Edu
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On Tue, 21 Feb 2006, Setoguchi, Soko,M.D. wrote:
Hi Kosuke,
I noticed that you updated MatchIt so that we can use our own distance measure.
So the argument I have to put in is
distance = pscore
Would you give me more detailed example?
For example, if I am using Lalonde data and I have created my propensity score
using a function that is not available within MatchIt. I predicted the
propensity score values by the function and named it as 'lalonde$ps'.
If I want to used this propensity score to match treated to control using
nearest method, what would the commands be exactly?
I guess I was not sure what to put in as a formula in the function of matchit.
I would guess you have to do something like
m.out <- matchit(treat ~ ????, data = lalonde, method = "nearest",
distance=ps)
Please let me know.
Soko
> -----Original Message-----
> From: owner-matchit(a)mail-1.hmdc.harvard.edu [mailto:owner-matchit@mail-
>
1.hmdc.harvard.edu] On Behalf Of Kosuke Imai
> Sent: Monday, December 19, 2005 4:11 PM
> To: Gary King
> Cc: Jeanie (Jie) Na; MatchIt Software Listserv
> Subject: Re: [matchit] Re: question abt MatchIt
>
> You can also use your own distance measure by
>
distance = pscore
>
> where pscore is a vector of your own distance measure.
>
> Kosuke
>
> ---------------------------------------------------------
> Kosuke Imai Office: Corwin Hall 041
> Assistant Professor Phone: 609-258-6601
> Department of Politics Fax: 973-556-1929
> Princeton University Email: kimai(a)Princeton.Edu
> Princeton, NJ 08544-1012
http://imai.princeton.edu
> ---------------------------------------------------------
>
>
> On Dec 19, 2005, at 2:00 PM, Gary King wrote:
>
> > On Fri, 16 Dec 2005, Jeanie (Jie) Na wrote:
> >
> >> Hi Dr. King,
> >>
> >> I am learning to use MatchIt package in R for a project I am
> >> working on.
> >> I have a couple of questions when I read about the manual.
> >>
> >> 1) I have a few categorical variables with multiple levels and a few
> >> continuous variables as covariates. The examples given in the
> >> manual of
> >> MatchIt seem to have all the covariates as dichotomous or
> >> continuous. Do
> >> I need to recode my data and give them values 1 to n (# of levels)?
> >> It doesnt seem to be ok as of now when I have character values for
> >> those
> >> categorical variables.
> >
> > you can exact match on fully category variables. otherwise, i
> > think you'd want to make them into 'continuous' variables as
you
> > would right side variables in a regression (such as a set of J-1
> > dummies coding J categories for a nominal variable)
> >
> >>
> >> 2) can you give me an example of the command if I want to use my own
> >> distance measure? What would be the input for distance? Will it be a
> >> distance matrix with rows for the treated,columns for the controlled,
> >> and values are the abs(logit(propensity score of control
> >> i)-logit(propensity score of treated j)). Or would it be a matrix
> >> with
> >> propensity scores as one column?
> >
> > the program allows you to estimate the distance based on
> > Mahalanobis distance or the propensity score computed in a variety
> > of ways. if you need different metrics you might need to explain
> > some more about what you're looking for.
> >
> > Best of luck,
> > Gary King
> >
> >>
> >> I hope I explained myself well. Thank you very much for your advice.
> >> --
> >> Jeanie (Jie) Na
> >>
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