search for: anova

## Question1: How to define IV with interaction alone, without main effects? ## Question2: Should Type III ANOVA in package car be independent of the factor level order? ## data from http://www.otago.ac.nz/sas/stat/chap30/sect52.htm drug <- c(t(t(rep(1,3)))%*%t(1:4)); disease <- c(t(t(1:3)) %*% t(rep(1,4))); y <- t(matrix(c( 42 ,44 ,36 ,13 ,19 ,22 ,33 ,NA ,26 ,NA ,33 ,21 ,31 ,-3 ,NA ,25 ,25 ,24...

Dear *, I have to perform an ANOVA analysis to study the effects on the performance of some algorithmic components in the design of my algorithm. I have done a full factorial design for the following 5 factors (my response variable is "best"): $ model :'data.frame': 3360 obs. of 6 variables: ....

...two categorical predictors and a continuous covariate (day) that I am using to model larval mass (l.mass): leaf.species has three levels - map, syc, and oak cond.time has two levels - 30 and 150. There are no response values for Map-150, so that entire, two-way, level is missing. When running anova() on the model with Type I SS, the full factorial design does not return errors; however, using package:car Anova() and Type III SS, I receive an singularity error unless I used the argument 'singular.ok = T' (it is defaulted to F). So, why don't I receive an error with anova() when...

...R> res1 <- lme(y~A+B, data=mydata, random=~1|subject) R> res2 <- lme(y~B+A, data=mydata, random=~1|subject) (only difference between these two models are the sequence in which the indep variables are written in formula) where y is continuous and A, B, and subject are factors. To get ANOVA table I used R> anova(res1) R> anova(res2) and found ANOVA tables corresponding to these two models are different. Is there any way I can get similar ANOVA tables from lme objects of this type?

I am trying to implement an ANOVA on a pair of quantile regression models in R. The anova.rq() function performs a basic check to see whether the models are nested, but I think this check is failing in my case. I think my models are nested despite the anova.rqlist() function saying otherwise. Here is an example where the GLM ANOVA...

Hello everyone, I've conducted a Type III repeated-measures ANOVA using Anova() from the car package, based on the suggestions at http://blog.gribblelab.org/2009/03/09/repeated-measures-anova-using-r/(option 3) and http://languagescience.umd.edu/wiki/EEG#ERP_ANOVA_in_R. My ANOVA has two factors: Condition (3 levels) and Region (6 levels) and their interaction. Be...

Given this interactive session: > an<-ls(pat="anova.ag.m2529") > an [1] "anova.ag.m2529.az" "anova.ag.m2529.can" "anova.ag.m2529.fl" > print(anova.ag.m2529.az) Analysis of Variance Table Response: year Df Sum Sq Mean Sq F value Pr(>F) time 1 14.823 14.8235 10.598 0....

Hi! as my subject says I am struggling with the different of a two-way ANOVA and a (two-way) ANCOVA. I found the following examples from this webpage: http://www.statmethods.net/stats/anova.html # One Way Anova (Completely Randomized Design) fit <- aov(y ~ A, data=mydataframe) # Randomized Block Design (B is the blocking factor) fit <- aov(y ~ A + B, data=mydataf...

...es: 0 ''***'' 0.001 ''**'' 0.01 ''*'' 0.05 ''.'' 0.1 '' '' 1 Residual standard error: 1.879 on 713 degrees of freedom Algorithm "port", convergence message: relative convergence (4) When I try to run the anova() function I get this: anova(fit.nls) Error in anova.nls(fit.nls) : anova is only defined for sequences of "nls" objects Could you tell me what the problem is? Thanks & Regards, Guru S [[alternative HTML version deleted]]

Hi, When I use Anova(car) to produce type III SS, 'Sum Sq' is reported in integers: > Anova(bot.lm3, type ="III") Anova Table (Type III tests) Response: bottemp Sum Sq Df F value Pr(>F) (Intercept) 45295 1 29436.4440 < 2e-16 fungroup...

Dear All -- I am trying to use within a little table producing code an anova comparison of two gls fitted objects, contained in a list of such object, obtained using nlme function gls. The anova procedure fails to locate the second of the objects. The following code, borrowed from the help page of anova.gls, exemplifies: --------------- start example code --------------- l...

Hi, I have an unbalanced dataset on which I would like to perform a one-way anova test using R (aov). According to Wannacott and Wannacott (1990) p. 333, one-way anova with unbalanced data is possible with a few modifications in the anova-calculations. The modified anova calculations should take into account different sample sizes and a modified definition of the average. I was...

Hey! Could you please take a quick look at what I have done? Somehow I get wrong results using the anova(lm()) combination compared to doing a two way ANOVA by hand. Running: Data<-read.table("Data.txt"); g<-lm(ExM~S1*S2,Data); anova(g); Gives: Analysis of Variance Table Response: ExM Df Sum Sq Mean Sq F value Pr(>F) S1 1 4.3679 4.3679 16...

Greetings, I am interested in creating a stepwise fixed order regression function. There's a function for this already called add1( ). The F statistics are calculated using type 2 anova (the SS and the F changes don't match SPSS's). You can see my use of this at the very end of the email. What I want: a function to make an anova table with f changes and delt R^2. I ran into 10 snags to making this a fully automated function using the full linear model (order matters...

Hi, For some reason do.call on anova fails if the models are named lmer objects. Consider the following example: library(lme4) models <- list( lmer(Reaction ~ Days + (1| Subject), sleepstudy), lmer(Reaction ~ Days + (Days | Subject), sleepstudy)) # # models is an unnamed list, do.call works (although with warning): do.call...

Hi R-listers, I am trying to do an ANOVA for the following scatterplot and received the following error: library(car) scatterplot(HSuccess ~ Veg, data = data.to.analyze, xlab = "Vegetation border (m)", ylab = "Hatching success (%)") anova(HSuccess ~ Veg, data=data.to.analyze) Er...

I would like to perform multiple comparisons or post-hoc testing on the independent variable in an Anova.mlm object generated by the Anova function of the car package. I have defined a multivariate linear model and subsequently performed a repeated measures ANOVA as per the instructions in section #3 of the following comprehensive tutorial on the subject from the Gribble lab at UWO: http://gribblelab...

There are anova {stats} and aov in R. It seems that anova takes an object returned by a model fitting function. But I don't see any examples for anova. Can somebody give me a simple example on anova? What is the difference between anova and aov?

...mbled across a mild glitch when trying to compare the result of gam() fitting with the result of lm() fitting. The following code demonstrates the problem: library(gam) x <- rep(1:10,10) set.seed(42) y <- rnorm(100) fit1 <- lm(y~x) fit2 <- gam(y~lo(x)) fit3 <- lm(y~factor(x)) print(anova(fit1,fit2)) # No worries. print(anova(fit1,fit3)) # Likewise. print(anova(fit2,fit3)) # Throws an error. print(anova(fit3,fit2)) # ``Works'' but gives negative degrees of freedom and sum of squares. Is this evidence of a ``bug''? Or am I being terribly young and naive to expec...

...act to soil treatment deppends on time? If soil F and D differed significantly in effects on plant biomass? If soil sterilization have any aditional effects on plant biomass in this experiment? Which is the most important factor for biomass accumulation? I can't figure out wether a repeated ANOVA or nested ANOVA, or a parallel one way ANOVA six times is right for this experiment. It seems not so feasible to run six paralle one way ANOVA for each plant and sampling date combination for the questions above. It takes me a long time to learn lme4 package in R, but till now fruitless. Would an...