Hi Bill, I have a feeling the sample is just too constrained and it’s just a really hard matching problem. I might recommend trying to do something like exact matching, like CEM (which would involve potentially coarsening the data, e.g., quintiles of the continuous variables). Liz On Apr 16, 2018, at 12:41 PM, William Dudley <wndudley@uncg.edu<mailto:wndudley@uncg.edu>> wrote: Matching experts, I am trying to match a small treatment group of schools (n = 3) with controls using a ratio of 1:4. I am using Mahal distance. The co variates are at the school level, but the analyses are planned at the student level. The match faces huge challenges to start with. The three treatment school are among the most extreme in the state with regard to the covariates: the highest dropout highest minority, highest poverty and lowest academic performance. I am getting warnings as follows: Warning messages: 1: glm.fit: algorithm did not converge 2: glm.fit: fitted probabilities numerically 0 or 1 occurred . I wonder if there are ways to work around the lack of convergence and fitted probabilities at the extreme. In previous work with this group I tried propensity scoring but that was equally problematic in term sof std differences. Thanks for any help. Bill On Mon, Feb 26, 2018 at 4:31 PM, <matchit-request@lists.gking.harvard.edu<mailto:matchit-request@lists.gking.harvard.edu>> wrote: Send Matchit mailing list submissions to matchit@lists.gking.harvard.edu<mailto:matchit@lists.gking.harvard.edu To subscribe or unsubscribe via the World Wide Web, visit https://lists.gking.harvard.edu/mailman/listinfo/matchit or, via email, send a message with subject or body 'help' to matchit-request@lists.gking.harvard.edu<mailto:matchit-request@lists.gking.harvard.edu You can reach the person managing the list at matchit-owner@lists.gking.harvard.edu<mailto:matchit-owner@lists.gking.harvard.edu When replying, please edit your Subject line so it is more specific than "Re: Contents of Matchit digest..." Today's Topics: 1. Re: MatchIt Question (Noah Greifer) ---------------------------------------------------------------------- Message: 1 Date: Mon, 26 Feb 2018 21:31:20 +0000 From: Noah Greifer <noah.greifer@gmail.com<mailto:noah.greifer@gmail.com>To: "Samadi, Mehrdad" <Mehrdad.Samadi@finra.org<mailto:Mehrdad.Samadi@finra.org>Cc: "matchit@lists.gking.harvard.edu<mailto:matchit@lists.gking.harvard.edu>" <matchit@lists.gking.harvard.edu<mailto:matchit@lists.gking.harvard.edu>Subject: Re: [matchit] MatchIt Question Message-ID: <CAPhhD8ma1szOPw9Zn_-5ber2E7jcovp9YgvK8cngT8bkVkrFxg@mail.gmail.com<mailto:CAPhhD8ma1szOPw9Zn_-5ber2E7jcovp9YgvK8cngT8bkVkrFxg@mail.gmail.com>Content-Type: text/plain; charset="utf-8" I'm not exactly sure what's going on with your code, but I think you could run the same analysis without splitting the data set and running 9 separate analyses just be setting exact = "stock" in a single matchit() call. Then match.data() could be run on the single output object. cobalt's bal.tab() can help examine balance on the separate groups. Noah On Mon, Feb 26, 2018 at 12:20 PM Samadi, Mehrdad <Mehrdad.Samadi@finra.org<mailto:Mehrdad.Samadi@finra.org>wrote: > Hi All, > I?ve been working with your MatchIT function in R and have a question: > I?m able to successfully run MatchIT on a list of dataframes using the > lapply function, which outputs a large list with a number of elements > corresponding to the number of separate MatchIT procedures that I ran, and > within each of these elements, 9 sub elements which correspond to the > standard output of MatchIt. > While I can successfully extract summary information from this MatchIt > large list using the summary function and lapply or sapply, I?m having > difficulty extracting the matrices of matched observations from each > separate MatchIt procedure. I get the error message, ?invalid subscript > type ?closure?. > Some more context is provide below, any insight that you have would be > helpful. Thanks for your time and consideration. > The raw dataframe ?sample? has the following structure: > *stock* > *firm* > *var* > *treated* > APPL > A > 0.5 > 1 > APPL > B > 0.54 > 0 > APPL > C > 0.33 > 0 > APPL > D > 0.38 > 0 > APPL > E > 0.88 > 0 > BAC > A > 0.5 > 0 > BAC > B > 0.54 > 1 > BAC > C > 0.33 > 0 > BAC > D > 0.38 > 0 > BAC > E > 0.88 > 0 > JPM > A > 0.5 > 0 > JPM > B > 0.54 > 1 > JPM > C > 0.33 > 0 > JPM > D > 0.38 > 0 > JPM > E > 0.88 > 0 > I want to use matchit for each stock separately, so I?m using a > combination of the split function and lapply: > X <- split(sample,sample$stock) > output <- lapply(names(X), function(n) { > matchit(treated ~ > var,data=X[[n]],method="nearest",distance="mahalanobis",replace=FALSE,ratio=1)}) > This would output a large list with 3 elements and within each of these 3 > elements, another 9 elements corresponding to MatchIt output. > I would like to extract the matrices corresponding to the matched > observations for each stock using match.data by again using lapply or > sapply, but get the following error: > sapply(output,match.data) > Error in X[[n]] : invalid subscript type 'closure' > Best, > Mehrdad > Confidentiality Notice:: This email, including attachments, may include > non-public, proprietary, confidential or legally privileged information. 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