Hi R users, I'm using the survey package to calculate summary statistics for a large health survey (the Demographic and Health Survey for Honduras, 2006), and when I try to calculate the variances for several variables, I get negative numbers. I thought it may be my data, so I ran the example on the help page:
data(api) ## one-stage cluster sample dclus1<-svydesign(id=~dnum, weights=~pw, data=apiclus1, fpc=~fpc) svyvar(~api00+enroll+api.stu+api99, dclus1) variance SE api00 11182.8 1386.4 api00 11516.3 1412.9 api.stu -4547.1 3164.9 api99 12735.2 1450.1 If I look at the full matrix for the variances (and covariances): test<-svyvar(~api00+enroll+api.stu+api99, dclus1) print(test, covariance=T) variance SE api00:api00 11182.8 1386.4 enroll:api00 -5492.4 3458.1 api.stu:api00 -4547.1 3164.9 api99:api00 11516.3 1412.9 api00:enroll -5492.4 3458.1 enroll:enroll 136424.3 41377.2 api.stu:enroll 114035.7 34153.9 api99:enroll -3922.3 3589.9 api00:api.stu -4547.1 3164.9 enroll:api.stu 114035.7 34153.9 api.stu:api.stu 96218.9 28413.7 api99:api.stu -3060.0 3260.9 api00:api99 11516.3 1412.9 enroll:api99 -3922.3 3589.9 api.stu:api99 -3060.0 3260.9 api99:api99 12735.2 1450.1 I see that the function is actually returning the covariance for the api.stu with the api00 variable. I can get the correct variances if I just take diag(test) But I just was wondering if anyone else was having this problem. I'm using : > sessionInfo() R version 2.10.1 Patched (2009-12-20 r50794) x86_64-apple-darwin9.8.0 locale: [1] en_US.UTF-8/en_US.UTF-8/C/C/en_US.UTF-8/en_US.UTF-8 attached base packages: [1] stats graphics grDevices utils datasets methods base other attached packages: [1] survey_3.19 loaded via a namespace (and not attached): [1] tools_2.10.1 And have the same error on a linux server. Thanks, Corey -- Corey Sparks Assistant Professor Department of Demography and Organization Studies University of Texas at San Antonio 501 West Durango Blvd Monterey Building 2.270C San Antonio, TX 78207 210-458-3166 corey.sparks 'at' utsa.edu https://rowdyspace.utsa.edu/users/ozd504/www/index.htm ______________________________________________ R-help@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.