Classification: UNCLASSIFIED Caveats: NONE R users, This is a summary for the responses I got from Sandra Dorai-Raj and Simon Blomberg followed by my question.
Sandra suggested using lm instead of lme for a model without a random effect, and Simon suggested anova.lme instead of anova.lm for comparing two models with and without a random effect. For the anova test, both anova.lme and anova work. Thanks again for their quick helpful responses. Kyong -----Original Message----- From: Park, Kyong H Mr ECBC Sent: Friday, March 14, 2008 3:26 PM To: '[email protected]' Subject: Lme does not work without a random effect (UNCLASSIFIED) Classification: UNCLASSIFIED Caveats: NONE Dear R users, I'm interested in finding a random effect of the Block in the data shown below, but 'lme' does not work without the random effect. I'm not sure how to group the data without continuous value which is shown in the error message at the bottom line. If I use 'aov' with Error(Block), is there a test method comparing between with and without the Block random effect. I'm using R 2.4.1. Appreciate your help. Kyong LCU ST1 SURF Block 1 6.71 A N 1 2 6.97 A Y 1 3 6.77 B N 1 4 6.90 B Y 1 5 6.63 C N 1 6 6.94 C Y 1 7 6.79 D N 1 8 6.93 D Y 1 9 6.23 A N 2 10 6.83 A Y 2 11 6.61 B N 2 12 6.86 B Y 2 13 6.51 C N 2 14 6.90 C Y 2 15 5.90 D N 2 16 6.97 D Y 2 A result with the random effect: Anal1<-lme(LCU~ST1*SURF,random=~1|Block,data=data1) > summary(Anal1) Linear mixed-effects model fit by REML Data: data1 AIC BIC logLik 25.38958 26.18399 -2.694789 Random effects: Formula: ~1 | Block (Intercept) Residual StdDev: 0.1421141 0.218483 Fixed effects: LCU ~ ST1 * SURF Value Std.Error DF t-value p-value (Intercept) 6.470 0.1842977 7 35.10625 0.0000 ST1B 0.220 0.2184830 7 1.00694 0.3475 ST1C 0.100 0.2184830 7 0.45770 0.6610 ST1D -0.125 0.2184830 7 -0.57213 0.5851 SURFY 0.430 0.2184830 7 1.96812 0.0897 ST1B:SURFY -0.240 0.3089816 7 -0.77675 0.4627 ST1C:SURFY -0.080 0.3089816 7 -0.25892 0.8031 ST1D:SURFY 0.175 0.3089816 7 0.56638 0.5888 Without the random effect: Anal2<-lme(LCU~ST1*SURF,data=data1) Error in getGroups.data.frame(dataMix, groups) : Invalid formula for groups Classification: UNCLASSIFIED Caveats: NONE Classification: UNCLASSIFIED Caveats: NONE [[alternative HTML version deleted]] ______________________________________________ [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 and provide commented, minimal, self-contained, reproducible code.
