Many thanks. I understand from your reply. Thanks.
At 2013-03-11 15:45:14,"PIKAL Petr" <petr.pi...@precheza.cz> wrote: >Hi > >> -----Original Message----- >> From: r-help-boun...@r-project.org [mailto:r-help-bounces@r- >> project.org] On Behalf Of meng >> Sent: Sunday, March 10, 2013 5:33 AM >> To: Greg Snow >> Cc: R help >> Subject: Re: [R] quesion about lm function >> >> Thanks for your reply. >> But the mean y of sex(f) and sex(m) can't be negative since the min and >> max of y is 1632.5 and 6410.6 respectively. >> >> And your code's result: >> >> sex(f): -1255.56 >> sex(m):-1118.73 >> >> The above result isn't correct since they are negative. > >You did not read the full advice. > > >> The tests are likely to be meaningless in this case and the means are >> the predicted means at x1=0 and x2=0 (so the means may make more sense >> if x1 and x2 are centered first). > >The above results (means) are correct at x1 and x2 = 0. > >result_lm <- lm(y~0+factor(sex) + scale(x1) + scale(x2), data=test) >coef(result_lm) >factor(sex)f factor(sex)m scale(x1) scale(x2) > 3876.6290 4013.4576 945.5634 592.7385 > >Anyway not a big difference from > >tapply(test$y, test$sex, mean) > f m >3790.760 4099.327 > >Regards >Petr > > >> >> Thanks >> >> >> >> >> >> >> >> >> >> At 2013-03-10 02:39:21,"Greg Snow" <538...@gmail.com> wrote: >> >> You can get the 2 means with: >> >> >> result_lm <- lm(y~0+factor(sex) + x1 + x2) >> >> >> The tests are likely to be meaningless in this case and the means are >> the predicted means at x1=0 and x2=0 (so the means may make more sense >> if x1 and x2 are centered first). >> >> >> >> On Sat, Mar 9, 2013 at 3:35 AM, meng <laomen...@163.com> wrote: >> Hi all: >> My data is in the attachment. >> I want to analysis the mean difference of y between 2 sex. >> >> My code: >> result_lm<-lm(y~factor(sex) + x1 + x2) >> summary(result_lm) >> >> The result of "factor(sex)m" 136.83, is the mean difference of y >> between 2 sex,and the corresponding p value is 0.07618. >> >> My question is: how to get the mean y of sex(m) and sex(f) respectively >> via lm function? >> >> Many thanks for your help. >> My best. >> >> >> ______________________________________________ >> 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. >> >> >> >> >> >> >> >> -- >> Gregory (Greg) L. Snow Ph.D. >> 538...@gmail.com >> [[alternative HTML version deleted]] >> >> ______________________________________________ >> 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. [[alternative HTML version deleted]] ______________________________________________ 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.
