I think that your problem comes from a misunderstanding. The general rule is that you give the plot command 2 vectors, x and y (though you can give it the vectors separately, or together in a list or matrix). If you give plot only a single vector then it will use this as the y vector and use the sequence of integers from 1 to the length of y as the x variable. Now in your example that matches your x exactly.
In your working examples you either give the function both x and y, or only y and the generated sequence for x happens to match your x for this specific example, but not in general. For your non-working examples you give only the x variable, which is then used as the y variable and the sequence is generated for x, so it will only identify points along the diagonal. It does not know where to find your y variable. The fix, always give both x and y (the fact that your examples worked with only y is due to your specific example, not anything general). -- Gregory (Greg) L. Snow Ph.D. Statistical Data Center Intermountain Healthcare greg.s...@imail.org 801.408.8111 > -----Original Message----- > From: r-help-boun...@r-project.org [mailto:r-help-boun...@r- > project.org] On Behalf Of casperyc > Sent: Tuesday, November 16, 2010 5:03 PM > To: r-help@r-project.org > Subject: [R] how exactly does 'identify' work? > > > Hi all, > > ######################################### > test=data.frame(x=1:26,y=-23.5+0.45*(1:26)+rnorm(26)) > rownames(test)=LETTERS[1:26] > attach(test) > #test > test.lm=lm(y~x) > > plot(test.lm,2) > identify(test.lm$res,,row.names(test)) > # not working > > plot(x,y) > identify(x,y,row.names(test)) > # works fine > identify(y,,row.names(test)) > # works fine > identify(x,,row.names(test)) > # not working > identify(y,,y) > # works > identify(x,,y) > # not working > > ##################################### > > My guess is that identify take the object 'x' ( the first argument ) is > the > thing that on the y axis. > > However, i have tried many many ways > trying to get the LETTERS to be identified in the QQ-plot > (plot(test.lm,2)) > it never works..... > > I have even tried to extract the standardized residual using > library(MASS), > the 'stdres' function, and put it as the first argument in identify, > still failed... > > Is there any means to achieve this? > > Thanks! > > casper > -- > View this message in context: http://r.789695.n4.nabble.com/how- > exactly-does-identify-work-tp3045953p3045953.html > Sent from the R help mailing list archive at Nabble.com. > > ______________________________________________ > 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. ______________________________________________ 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.
