this is documented: check ?"[". You need to specify drop = FALSE, i.e.,
is.matrix(y[-c(1,2,3), , drop = FALSE]) Best, Dimitris ---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/(0)16/336899 Fax: +32/(0)16/337015 Web: http://www.med.kuleuven.be/biostat/ http://www.student.kuleuven.be/~m0390867/dimitris.htm ----- Original Message ----- From: <[EMAIL PROTECTED]> To: "Gabor Grothendieck" <[EMAIL PROTECTED]> Cc: "Brian Quinif" <[EMAIL PROTECTED]>; <[email protected]>; <[EMAIL PROTECTED]> Sent: Friday, April 07, 2006 3:16 PM Subject: [R] strange matrix behaviour: is there a matrix with one row? > Consider this: > >> y <- matrix(1:8, ncol=2) >> is.matrix(y[-c(1,2),]) > [1] TRUE >> is.matrix(y[-c(1,2,3),]) > [1] FALSE >> is.matrix(y[-c(1,2,3,4),]) > [1] TRUE > > It seems like an inconsistent behaviour: > - with 2 or more rows we have a matrix > - with 1 row we do not have a matrix and > - with 0 rows we have a matrix again > > I just stumbled on this behaviour, because I had a problem > with my program in which I have assumed that matrix with > some rows removed is still a matrix, which seems to be mostly > true, but it is not true if only one row is left. > > Comments? Suggestions? > How to work around this problem - without to many "if" statements? > > Best regards, > Ryszard > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > Disclaimer: http://www.kuleuven.be/cwis/email_disclaimer.htm ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
