Dear R developers, In the help text for ave() you can read in Arguments section: "... Grouping variables, typically factors, all of the same length as x" ...and in Value: "If ... is g1,g2,". I think a description in the Arguments section of how two or more grouping variables is specified together with an Example would be very helpful. In absence of a help text I just tried if the equivalent specification in tapply would work: data(warpbreaks) str(warpbreaks) 'data.frame': 54 obs. of 3 variables: $ breaks : num 26 30 54 25 70 52 51 26 67 18 ... $ wool : Factor w/ 2 levels "A","B": 1 1 1 1 1 1 1 1 1 1 ... $ tension: Factor w/ 3 levels "L","M","H": 1 1 1 1 1 1 1 1 1 2 ... ave(x = breaks, list(wool, tension), FUN = median) Is this THE way to specify two or more grouping variables in ave()? If yes, maybe it could be used as an example. Thank you all for your great work developing R!
Henrik P?rn Centre for Conservation Biology Department of Biology Norwegian University of Science and Technology NO-7491 Trondheim Norway Office: +47 73596285 Fax: +47 73596100 Mobile: +47 90989255 E-mail: henrik.parn at bio.ntnu.no