Dear R People: I have the following in a file: resp factA factB 39.5 low B- 38.6 high B- 27.2 low B+ 24.6 high B+ 43.1 low B- 39.5 high B- 23.2 low B+ 24.2 high B+ 45.2 low B- 33.0 high B- 24.8 low B+ 22.2 high B+ and I construct the data frame:> collard.df <- read.table("collard.txt",header=TRUE) > collard.aov <- aov(resp~factA*factB,data=collard.df) > summary(collard.aov)Df Sum Sq Mean Sq F value Pr(>F) factA 1 36.4 36.4 5.511 0.0469 * factB 1 716.1 716.1 108.419 6.27e-06 *** factA:factB 1 13.0 13.0 1.971 0.1979 Residuals 8 52.8 6.6 --- Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1> tapply(collard.df$resp,list(collard.df$factA,collard.df$factB),mean)B- B+ high 37.03333 23.66667 low 42.60000 25.06667>Fair enough. Let's pretend for a second that interaction existed. Then I want to set up contrasts such that mean(high) - mean(low) = 0 and mean(B+) - mean(B-) = 0. I know that this is really simple, but I've tried all kinds of things with glht and am not sure that I'm on the right track. Sorry for the trouble for the simple question. Thanks, erin -- Erin Hodgess Associate Professor Department of Computer and Mathematical Sciences University of Houston - Downtown mailto: erinm.hodgess@gmail.com [[alternative HTML version deleted]]
I found the solution: stats.stackexchange.com/questions/12993/how-to-setup-and-interpret-anova-contrasts-with-the-car-package-in-r Sorry for the trouble. On Sun, Mar 24, 2013 at 8:58 PM, Erin Hodgess <erinm.hodgess@gmail.com>wrote:> Dear R People: > > I have the following in a file: > > resp factA factB > 39.5 low B- > 38.6 high B- > 27.2 low B+ > 24.6 high B+ > 43.1 low B- > 39.5 high B- > 23.2 low B+ > 24.2 high B+ > 45.2 low B- > 33.0 high B- > 24.8 low B+ > 22.2 high B+ > > and I construct the data frame: > > > collard.df <- read.table("collard.txt",header=TRUE) > > collard.aov <- aov(resp~factA*factB,data=collard.df) > > summary(collard.aov) > Df Sum Sq Mean Sq F value Pr(>F) > factA 1 36.4 36.4 5.511 0.0469 * > factB 1 716.1 716.1 108.419 6.27e-06 *** > factA:factB 1 13.0 13.0 1.971 0.1979 > Residuals 8 52.8 6.6 > --- > Signif. codes: 0 ‘***’ 0.001 ‘**’ 0.01 ‘*’ 0.05 ‘.’ 0.1 ‘ ’ 1 > > tapply(collard.df$resp,list(collard.df$factA,collard.df$factB),mean) > B- B+ > high 37.03333 23.66667 > low 42.60000 25.06667 > > > > Fair enough. Let's pretend for a second that interaction existed. Then I > want to set up contrasts such that mean(high) - mean(low) = 0 and mean(B+) > - mean(B-) = 0. > > I know that this is really simple, but I've tried all kinds of things with > glht and am not sure that I'm on the right track. Sorry for the trouble > for the simple question. > > Thanks, > erin > > > > > -- > Erin Hodgess > Associate Professor > Department of Computer and Mathematical Sciences > University of Houston - Downtown > mailto: erinm.hodgess@gmail.com-- Erin Hodgess Associate Professor Department of Computer and Mathematical Sciences University of Houston - Downtown mailto: erinm.hodgess@gmail.com [[alternative HTML version deleted]]