birgitle birgitlemckesystbotuzhch many thanks mark answer seems possible use variables without somehow imputing missing values try variables finally use many thanks b mark difford wrote hi birgitle seems failing columns single entry ie 1 rest 0 1 0s gets reasons failure call get positive definite matrix main problem lies calculation standard errors combinations get result columns turning get standard errors columns 60 omitting columns 12 23 44 need work rest columning forwards till get failure drop column index probably isnt enough information calculate ses columns cause error works default settings without columns 12 23 44 hetcortestpartc1111322244345 pdt stderrt usecompleteobs first fails second works hetcortestpartc111132224434560 pdt stderrf hetcortestpartc172 pdf stderrf hth mark art living like wrestling dancing marcus aurelius view message context httpwwwnabblecomproblemsusinghetcor28polycor29tp18867343p18870543html sent r help mailing list archive nabblecom ______________________________________________ rhelprprojectorg mailing list httpsstatethzchmailmanlistinforhelp please read posting guide httpwwwrprojectorgpostingguidehtml provide commented minimal selfcontained reproducible code thu 07 aug 2008 062951 0700 r problems using hetcor polycor