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| From | njcoxstata@gmail.com |
| To | "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu> |
| Subject | Re: st: Missing observations |
| Date | Thu, 20 Jun 2013 18:29:32 +0100 |
This is really isn't clear to me, but it may be that -var1- and -var2- should be stacked on top of each other. Nick njcoxstata@gmail.com On 20 Jun 2013, at 15:41, Csaba <csaba.kertai@hotmail.co.uk> wrote: > Nick, > > Thank you for your reply. Yes you are right I muddled up observations with values. I meant to write values not observations. My problem is that if I use 'drop if missing(var2)' that will drop values for each variable in my data set. > > I need to compare the means/medians of 2 variables. Var1 has 1125 non-missing values, var2 has 169 non-missing values. I might be doing sth wrong but when I try using bootstrapping I get a message saying that I should drop any missing values as bootstrapping cannot distinguish between missing and non-missing values. That's why I want to drop missing values for Var2. Basically, I want to achieve the same result as with the unpaired two-sample mean comparison test but with bootstrapping. > > Thanks a lot! > > On 20 Jun 2013, at 12:32, Nick Cox <njcoxstata@gmail.com> wrote: > >> -drop- as used here drops entire observations (outside Stata >> observations are known as rows, cases, records). You seem to be under >> the impression that there is an operation >> >> drop missing values >> >> that is somehow different from >> >> -drop- observations >> >> but I don't know what that would look like. >> >> In your example if -var2- has only 169 non-missing values (_not_ >> observations) then >> >> drop if missing(var2) >> >> will leave precisely 169 observations. I don't understand how that is >> a surprise or what else you want. >> >> Nick >> njcoxstata@gmail.com >> >> >> On 20 June 2013 11:17, Csaba Kertai <csaba.kertai@hotmail.co.uk> wrote: >> >>> I need a bit of help with dropping missing observations. If I use 'drop if missing(var)' or drop if 'var'==. etc. many other observations are dropped as well. More precisely, var1 has 1125 observations and var2 has 169 observations. I want to drop missing observations for var2 but if I use drop if var2==. then this will keep only 169 observations for each variable. I only want to drop values that are missing. >> >> * >> * For searches and help try: >> * http://www.stata.com/help.cgi?search >> * http://www.stata.com/support/faqs/resources/statalist-faq/ >> * http://www.ats.ucla.edu/stat/stata/ > > * > * For searches and help try: > * http://www.stata.com/help.cgi?search > * http://www.stata.com/support/faqs/resources/statalist-faq/ > * http://www.ats.ucla.edu/stat/stata/ * * For searches and help try: * http://www.stata.com/help.cgi?search * http://www.stata.com/support/faqs/resources/statalist-faq/ * http://www.ats.ucla.edu/stat/stata/