Re: [R] Cross-over Data with Kenward-Roger correction
On 08 Jun 2015, at 22:59 , Ben Bolker bbol...@gmail.com wrote: As a statistical point, I don't understand why you can't just do a paired t-test on these data?? It's a cross-over trial, so you need to account for the period effect. However, a standard way of treating it is by to calculate period differences within subjects and use a t-test (welch or classical) to see if the differ according to sequence (trt1-trt2 or v.v.). -- Peter Dalgaard, Professor, Center for Statistics, Copenhagen Business School Solbjerg Plads 3, 2000 Frederiksberg, Denmark Phone: (+45)38153501 Office: A 4.23 Email: pd@cbs.dk Priv: pda...@gmail.com __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
Re: [R] Cross-over Data with Kenward-Roger correction
knouri nouri4 at yahoo.com writes: Dear all:for the folowing data, a two-period, two treatment (A=1 vs. B=2) cross-over is fitted using the folowing SAS code. data one; [snip] run; proc mixed data=one method=reml; class Sbj Per Trt; model PEF = Per Trt /ddfm=kr; repeated Trt / sub=Sbj type=un r; lsmeans Trt / cl alpha=0.05; estimate 'B vs. A' Trt -1 1 / alpha=0.1 cl; run; (where kr option is for Kenward-Roger method).I need to use R to reproduce the results similar to what the above SAS code generates. I have used several R functions including lme, lmer with no success so far.Any advice will be greatly appreciated,Sincerely, Keramat This is more appropriate for r-sig-mixed-mod...@r-project.org. Please post followups there. The lmerTest and lsmeans packages will probably be useful. As a statistical point, I don't understand why you can't just do a paired t-test on these data?? dat - read.table(header=TRUE,text= Sbj Seq Per Trt PEF 1 1 1 1 310 1 1 2 2 270 4 1 1 1 310 4 1 2 2 260 6 1 1 1 370 6 1 2 2 300 7 1 1 1 410 7 1 2 2 390 10 1 1 1 250 10 1 2 2 210 11 1 1 1 380 11 1 2 2 350 14 1 1 1 330 14 1 2 2 365 2 2 1 2 370 2 2 2 1 385 3 2 1 2 310 3 2 2 1 400 5 2 1 2 380 5 2 2 1 410 9 2 1 2 290 9 2 2 1 320 12 2 1 2 260 12 2 2 1 340 13 2 1 2 90 13 2 2 1 220) library(lmerTest) library(ggplot2); theme_set(theme_bw()) ggplot(dat,aes(x=Per,y=PEF,colour=factor(Trt)))+geom_point()+ geom_line(colour=gray,aes(group=Sbj))+ scale_x_continuous(breaks=c(1,2)) m1 - lmer(PEF~Per+Trt +(Trt|Sbj), data=dat) ## warning about unidentifiability __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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] Cross-over Data with Kenward-Roger correction
Dear all:for the folowing data, a two-period, two treatment (A=1 vs. B=2) cross-over is fitted using the folowing SAS code. data one; input Sbj Seq Per Trt PEF; cards; 1 1 1 1 310 1 1 2 2 270 4 1 1 1 310 4 1 2 2 260 6 1 1 1 370 6 1 2 2 300 7 1 1 1 410 7 1 2 2 390 10 1 1 1 250 10 1 2 2 210 11 1 1 1 380 11 1 2 2 350 14 1 1 1 330 14 1 2 2 365 2 2 1 2 370 2 2 2 1 385 3 2 1 2 310 3 2 2 1 400 5 2 1 2 380 5 2 2 1 410 9 2 1 2 290 9 2 2 1 320 12 2 1 2 260 12 2 2 1 340 13 2 1 2 90 13 2 2 1 220 ; run; proc mixed data=one method=reml; class Sbj Per Trt; model PEF = Per Trt /ddfm=kr; repeated Trt / sub=Sbj type=un r; lsmeans Trt / cl alpha=0.05; estimate 'B vs. A' Trt -1 1 / alpha=0.1 cl; run; (where kr option is for Kenward-Roger method).I need to use R to reproduce the results similar to what the above SAS code generates. I have used several R functions including lme, lmer with no success so far.Any advice will be greatly appreciated,Sincerely, Keramat [[alternative HTML version deleted]] __ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see 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.
