Try using the noimbal option. You won’t get the error, and there is no reason why this would prevent –cem- from calculating the weights.
Here is my code as an example:
. cem gender age cci_score, tr( ord_treat) noimbal
Matching Summary:
-----------------
Number of strata: 220
Number of matched strata: 36
0 1 2 3 .
All 6612 344 194 116 705
Matched 3146 179 105 79 375
Unmatched 3466 165 89 37 330
From: cem-bounces@lists.gking.harvard.edu [mailto:cem-bounces@lists.gking.harvard.edu] On Behalf Of Erik Cleven
Sent: Wednesday, November 11, 2015 4:21 PM
Cc: cem@lists.gking.harvard.edu
Subject: Re: [cem] cem error message
Thanks, Ariel!
Because of the error message cem does not calculate cem_weights. I am therefore not able to run a regression model after cem preprocessing the data.
I assume that when you have more than two treatments is it correct to use one treatment variable that is coded as a categorical variable, right?
Erik
On Wed, Nov 11, 2015 at 4:06 PM, Ariel Linden <ariel.linden@gmail.com> wrote:
You can certainly specify more than 2 treatments. The error you’re getting is because –imbalance- is set up to compare between only two treatment groups. As for the k2k error, I don’t get that error. However, I do find that k2k does not produce 1:1 matches when there are more than two treatments.
From: cem-bounces@lists.gking.harvard.edu [mailto:cem-bounces@lists.gking.harvard.edu] On Behalf Of Erik Cleven
Sent: Wednesday, November 11, 2015 3:59 PM
To: cem@lists.gking.harvard.edu
Subject: [cem] cem error message
I am attempting to run cem with an ordinal treatment variable that has four values. I get the following error message:
imbalance(): 3258 <tmp>[1,1] found where void required
<istmt>: - function returned error
r(3258);
A previous reply to someone who also got this error message said to update cem because there was a bug with the imb function.
I updated and now recieve this message:
NOTE: Treatment has must have only 2 levels to compute distance and weights. In addition, k2k cannot be used.
Does this mean cem cannot be used with more than 2 treatments? Actually I have a continuous treatment but I recoded it to a variable with four levels.
Thanks!
Erik
--
Erik Cleven, PhD
Assistant Professor
Department of Politics
Saint Anselm College
100 Saint Anselm Drive
Manchester, NH 03102-1310
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Erik Cleven, PhD
Assistant Professor
Department of Politics
Saint Anselm College
100 Saint Anselm Drive
Manchester, NH 03102-1310