So the matching worked, just not –imbalance- … I’ll have to Let Matt Blackwell field this error. From: Dennis Hanseman [mailto:hanseman@one.net] Sent: Thursday, July 24, 2014 8:51 PM To: 'Ariel Linden'; cem(a)lists.gking.harvard.edu Subject: RE: [cem] Error when using cem with >2 treatments Tried that, but got the error message again: . cem margins1 age if approach1 != . , tr(approach1) Matching Summary: ----------------- Number of strata: 28 Number of matched strata: 24 1 2 3 All 457 6352 2444 Matched 457 6292 2427 Unmatched 0 60 17 imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error r(3258); Dennis From: Ariel Linden [mailto:ariel.linden@gmail.com] Sent: Thursday, July 24, 2014 8:09 PM To: Dennis Hanseman; cem(a)lists.gking.harvard.edu Subject: Re: [cem] Error when using cem with >2 treatments Your "if" statement needs to come before the comma Ariel From: Dennis Hanseman Sent: Thursday, July 24, 2014 8:01 PM To: cem(a)lists.gking.harvard.edu Subject: [cem] Error when using cem with >2 treatments I’m trying to use cem to do matching involving 3 treatments. Prof. King (http://comments.gmane.org/gmane.comp.lang.r.matchit/393) indicated that this can be done. When I tried it, I got an error message – imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error There was a discussion on this site on July 24 of 2013 about a similar issue. In that case, there were only 2 treatments but a treatment of “.”, along with “1” and “2”, showed up in the summary table. The suggestion was to add “if indepvote != ." to the cem call.” While I’m sure that there are no missing values of my treatment variable, I still tried to add the if clause to my cem call. But it didn’t help. I got another error: . cem margins1 age, tr(approach1) if approach1 != . option if not allowed r(198); Any ideas of how I can proceed? Thanks. Dennis Hanseman

Thanks, but I’m still encountering problems. I ran this code: use "D:\Documents\Midura Paquette\6.16.14 NCDB - Rectal CA only.dta", clear generate approach1 = 1 replace approach1 = 2 if approach == "open" replace approach1 = 3 if approach == "laparoscopic" generate margins1 = 1 replace margins1 = 0 if margins == "negative" drop if approach1 == . summarize margins1 age approach1 logistic margins1 i.approach1 cem margins1 age, tr(approach1) and got this output: . do "C:\Users\Hanseman\AppData\Local\Temp\STD00000000.tmp" . use "D:\Documents\Midura Paquette\6.16.14 NCDB - Rectal CA only.dta", clear . . generate approach1 = 1 . replace approach1 = 2 if approach == "open" (6352 real changes made) . replace approach1 = 3 if approach == "laparoscopic" (2444 real changes made) . . generate margins1 = 1 . replace margins1 = 0 if margins == "negative" (8512 real changes made) . . drop if approach1 == . (0 observations deleted) . summarize margins1 age approach1 Variable | Obs Mean Std. Dev. Min Max -------------+------------------------------------------------------------------------ margins1 | 9253 .0800821 .271435 0 1 age | 9253 62.45888 13.09845 18 90 approach1 | 9253 2.214741 .5171413 1 3 . logistic margins1 i.approach1 Logistic regression Number of obs = 9253 LR chi2(2) = 21.80 Prob > chi2 = 0.0000 Log likelihood = -2570.4092 Pseudo R2 = 0.0042 ------------------------------------------------------------------------------ margins1 | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval] -------------+-------------------------------------------------------------------------------------------- approach1 | 2 | 1.754614 .3760161 2.62 0.009 1.152837 2.670516 3 | 1.213282 .273746 0.86 0.392 .7796687 1.88805 | _cons | .0554273 .0116234 -13.79 0.000 .036747 .0836035 ------------------------------------------------------------------------------ . cem margins1 age, tr(approach1) Matching Summary: ----------------- Number of strata: 28 Number of matched strata: 24 1 2 3 All 457 6352 2444 Matched 457 6292 2427 Unmatched 0 60 17 imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error r(3258); end of do-file r(3258); . This is a mystery to me. Do you have other ideas as to what might be going wrong. Thanks for your help. Dennis Hanseman From: Matt Blackwell [mailto:mblackwell@gov.harvard.edu] Sent: Friday, July 25, 2014 8:32 AM To: Ariel Linden Cc: Dennis Hanseman; cem(a)lists.gking.harvard.edu Subject: Re: [cem] Error when using cem with >2 treatments Hi Dennis, We need to implement an "if" syntax for the imbalance command, but it's still a work in progress. For now, you can simply subset the data to non-missing treatments: drop if approach1 != . That should solve the error. Cheers, Matt ~~~~~~~~~~~ Matthew Blackwell Assistant Professor of Government Harvard University url: http://www.mattblackwell.org On Thu, Jul 24, 2014 at 9:09 PM, Ariel Linden &lt;ariel.linden(a)gmail.com&gt; wrote: So the matching worked, just not –imbalance- … I’ll have to Let Matt Blackwell field this error. From: Dennis Hanseman [mailto:hanseman@one.net] Sent: Thursday, July 24, 2014 8:51 PM To: 'Ariel Linden'; cem(a)lists.gking.harvard.edu Subject: RE: [cem] Error when using cem with >2 treatments Tried that, but got the error message again: . cem margins1 age if approach1 != . , tr(approach1) Matching Summary: ----------------- Number of strata: 28 Number of matched strata: 24 1 2 3 All 457 6352 2444 Matched 457 6292 2427 Unmatched 0 60 17 imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error r(3258); Dennis From: Ariel Linden [mailto:ariel.linden@gmail.com] Sent: Thursday, July 24, 2014 8:09 PM To: Dennis Hanseman; cem(a)lists.gking.harvard.edu Subject: Re: [cem] Error when using cem with >2 treatments Your "if" statement needs to come before the comma Ariel From: Dennis Hanseman Sent: Thursday, July 24, 2014 8:01 PM To: cem(a)lists.gking.harvard.edu Subject: [cem] Error when using cem with >2 treatments I’m trying to use cem to do matching involving 3 treatments. Prof. King (http://comments.gmane.org/gmane.comp.lang.r.matchit/393) indicated that this can be done. When I tried it, I got an error message – imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error There was a discussion on this site on July 24 of 2013 about a similar issue. In that case, there were only 2 treatments but a treatment of “.”, along with “1” and “2”, showed up in the summary table. The suggestion was to add “if indepvote != ." to the cem call.” While I’m sure that there are no missing values of my treatment variable, I still tried to add the if clause to my cem call. But it didn’t help. I got another error: . cem margins1 age, tr(approach1) if approach1 != . option if not allowed r(198); Any ideas of how I can proceed? Thanks. Dennis Hanseman - -- cem Mailing List, served by HUIT Send messages: cem(a)lists.gking.harvard.edu [un]subscribe Options: http://lists.gking.harvard.edu/?info=cem More information on cem: http://gking.harvard.edu/cem Cem mailing list Cem(a)lists.gking.harvard.edu To unsubscribe from this list or get other information: https://lists.gking.harvard.edu/mailman/listinfo/cem

Don’t forget the “replace” on the last line: net install cem, replace Ariel From: Matt Blackwell [mailto:mblackwell@gov.harvard.edu] Sent: Sunday, September 21, 2014 10:28 AM To: Dennis Hanseman Cc: Ariel Linden; cem(a)lists.gking.harvard.edu Subject: Re: [cem] Error when using cem with >2 treatments Hi Dennis, Sorry for the late reply. It turns out that this was a bug with the imb function that didn't affect the matching results at all. CEM should have just omitted the imbalance results since we don't have a straightforward way to calculate imbalance with more than 2 treatment groups. In the latest version of cem (1.3), this works appropriately. You can update using the folllowing commands: ado uninstall cem net from http://www.mattblackwell.org/files/stata net install cem (you may need to use ", force" at the end the last command) Hope that helps! Cheers, Matt On Fri, Jul 25, 2014 at 1:25 PM, Dennis Hanseman &lt;hanseman(a)one.net&gt; wrote: Thanks, but I’m still encountering problems. I ran this code: use "D:\Documents\Midura Paquette\6.16.14 NCDB - Rectal CA only.dta", clear generate approach1 = 1 replace approach1 = 2 if approach == "open" replace approach1 = 3 if approach == "laparoscopic" generate margins1 = 1 replace margins1 = 0 if margins == "negative" drop if approach1 == . summarize margins1 age approach1 logistic margins1 i.approach1 cem margins1 age, tr(approach1) and got this output: . do "C:\Users\Hanseman\AppData\Local\Temp\STD00000000.tmp" . use "D:\Documents\Midura Paquette\6.16.14 NCDB - Rectal CA only.dta", clear . . generate approach1 = 1 . replace approach1 = 2 if approach == "open" (6352 real changes made) . replace approach1 = 3 if approach == "laparoscopic" (2444 real changes made) . . generate margins1 = 1 . replace margins1 = 0 if margins == "negative" (8512 real changes made) . . drop if approach1 == . (0 observations deleted) . summarize margins1 age approach1 Variable | Obs Mean Std. Dev. Min Max -------------+------------------------------------------------------------------------ margins1 | 9253 .0800821 .271435 0 1 age | 9253 62.45888 13.09845 18 90 approach1 | 9253 2.214741 .5171413 1 3 . logistic margins1 i.approach1 Logistic regression Number of obs = 9253 LR chi2(2) = 21.80 Prob > chi2 = 0.0000 Log likelihood = -2570.4092 Pseudo R2 = 0.0042 ------------------------------------------------------------------------------ margins1 | Odds Ratio Std. Err. z P>|z| [95% Conf. Interval] -------------+-------------------------------------------------------------------------------------------- approach1 | 2 | 1.754614 .3760161 2.62 0.009 1.152837 2.670516 3 | 1.213282 .273746 0.86 0.392 .7796687 1.88805 | _cons | .0554273 .0116234 -13.79 0.000 .036747 .0836035 ------------------------------------------------------------------------------ . cem margins1 age, tr(approach1) Matching Summary: ----------------- Number of strata: 28 Number of matched strata: 24 1 2 3 All 457 6352 2444 Matched 457 6292 2427 Unmatched 0 60 17 imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error r(3258); end of do-file r(3258); . This is a mystery to me. Do you have other ideas as to what might be going wrong. Thanks for your help. Dennis Hanseman From: Matt Blackwell [mailto:mblackwell@gov.harvard.edu] Sent: Friday, July 25, 2014 8:32 AM To: Ariel Linden Cc: Dennis Hanseman; cem(a)lists.gking.harvard.edu Subject: Re: [cem] Error when using cem with >2 treatments Hi Dennis, We need to implement an "if" syntax for the imbalance command, but it's still a work in progress. For now, you can simply subset the data to non-missing treatments: drop if approach1 != . That should solve the error. Cheers, Matt ~~~~~~~~~~~ Matthew Blackwell Assistant Professor of Government Harvard University url: http://www.mattblackwell.org On Thu, Jul 24, 2014 at 9:09 PM, Ariel Linden &lt;ariel.linden(a)gmail.com&gt; wrote: So the matching worked, just not –imbalance- … I’ll have to Let Matt Blackwell field this error. From: Dennis Hanseman [mailto:hanseman@one.net] Sent: Thursday, July 24, 2014 8:51 PM To: 'Ariel Linden'; cem(a)lists.gking.harvard.edu Subject: RE: [cem] Error when using cem with >2 treatments Tried that, but got the error message again: . cem margins1 age if approach1 != . , tr(approach1) Matching Summary: ----------------- Number of strata: 28 Number of matched strata: 24 1 2 3 All 457 6352 2444 Matched 457 6292 2427 Unmatched 0 60 17 imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error r(3258); Dennis From: Ariel Linden [mailto:ariel.linden@gmail.com] Sent: Thursday, July 24, 2014 8:09 PM To: Dennis Hanseman; cem(a)lists.gking.harvard.edu Subject: Re: [cem] Error when using cem with >2 treatments Your "if" statement needs to come before the comma Ariel From: Dennis Hanseman Sent: Thursday, July 24, 2014 8:01 PM To: cem(a)lists.gking.harvard.edu Subject: [cem] Error when using cem with >2 treatments I’m trying to use cem to do matching involving 3 treatments. Prof. King (http://comments.gmane.org/gmane.comp.lang.r.matchit/393) indicated that this can be done. When I tried it, I got an error message – imbalance(): 3258 <tmp>[1,1] found where void required <istmt>: - function returned error There was a discussion on this site on July 24 of 2013 about a similar issue. In that case, there were only 2 treatments but a treatment of “.”, along with “1” and “2”, showed up in the summary table. The suggestion was to add “if indepvote != ." to the cem call.” While I’m sure that there are no missing values of my treatment variable, I still tried to add the if clause to my cem call. But it didn’t help. I got another error: . cem margins1 age, tr(approach1) if approach1 != . option if not allowed r(198); Any ideas of how I can proceed? Thanks. Dennis Hanseman - -- cem Mailing List, served by HUIT Send messages: cem(a)lists.gking.harvard.edu [un]subscribe Options: http://lists.gking.harvard.edu/?info=cem More information on cem: http://gking.harvard.edu/cem Cem mailing list Cem(a)lists.gking.harvard.edu To unsubscribe from this list or get other information: https://lists.gking.harvard.edu/mailman/listinfo/cem