search for: aov

Displaying 20 results from an estimated 334 matches for "aov".

2007 Jan 15
3
model simplification in repeated anova
Hi, I''ve done a repeated ANOVA looking as follows: model<-aov(y~a*b*c+Error(d)) Now I want to get rid of some or all of the interactions. But neither AIC nor anova work. What is the appropriate function to test my model?
2008 May 28
5
Tukey HSD (or other post hoc tests) following repeated measures ANOVA
...that even I could understand... ;-) Now, I want to calculate a post-hoc test following up a within-subjects ANOVA. The dv is reaction time (RT), there is a 3-level Condition factor (Cond; within-subjects), a number of subjects (Subj), and the dataframe is called WMU3C. The model is > RT.aov <- aov(RT~Cond + Error(Subj/Cond), WMU3C) I understand that TukeyHSD only works with an aov object, but that RT.aov is an aovlist object. > class(RT.aov) [1] "aovlist" "listof" I''ve tried to work around it using the "maiz" example in the MMC do...
2003 Oct 15
3
aov and non-categorical variables
It is unclear to me how aov() handles non-categorical variables. I mean it works and produces results that I would expect, but I was under impression that ANOVA is only defined for categorical variables. In addition, help(aov) says that it "call to ''lm'' for each stratum", which I presume means...
2002 Jul 05
2
balance in AoV (was aov() and NaN)
<ripley at stats.ox.ac.uk> wrote: > Hint 2: in the absence of balance, ...., and lme can do that Would it be possible to make aov like wrappers to the various special lm variants allowing for a uniform syntax for anova? aov(resp~f1*f2+Error(S/(f1*f2))) ## uses lm aov.lme(resp~f1*f2+Error(S/(f1*f2))) ## uses lme aov.rlm(resp~f1*f2+Error(S/(f1*f2))) ## uses rlm ... I''d do it, but I do not nearly understa...
2002 Sep 06
2
Using Anova Sums of Squares
Dear all, I''m trying to access the Sums of Squares resulting from a summary(aov(....)) so I can use them in a function. Is there an easy way to access these? The structure of a summary.aov object is something like this: > str(summary(fhc.aov)) List of 5 $ Error: PPNR :List of 1 ..$ :Classes anova and `data.frame'': 1 obs. of 5 variables: .. ..$ Df...
2013 Mar 06
3
aov() and anova() making faulty F-tests
Dear useRs, I''ve just encountered a serious problem involving the F-test being carried out in aov() and anova(). In the provided example, aov() is not making the correct F-test for an hypothesis involving the expected mean square (EMS) of a factor divided by the EMS of another factor (i.e., instead of the error EMS). Here is the example: Expected Mean Square df...
2002 Jul 05
3
aov() and NaN
hi, another anova question !! how does aov() treat missing values ? since it might depend on my experimental design: i have a within subject design with two factors ... i use aov() like this: aov(performance~type*block+Error(subj/(type+block)),data=anovaData) now it might happen that i have a couple of NaN data points in my result...
2006 Aug 03
3
between-within anova: aov and lme
I have 2 questions on ANOVA with 1 between subjects factor and 2 within factors. 1. I am confused on how to do the analysis with aov because I have seen two examples on the web with different solutions. a) Jon Baron (http://www.psych.upenn.edu/~baron/rpsych/rpsych.html) does 6.8.5 Example 5: Stevens pp. 468 - 474 (one between, two within) between: gp within: drug, dose aov(effect ~ gp * drug * dose + Error(...
2010 Sep 29
4
Problems extracting p-value from summary(aov(...))
Hi, I did a aov and used summary to obtain the p-value. I tried many ways to extract the p-value from the summary result but failed. Among others I tried the following: > test.summary <- > summary(aov(data[,1]~time.points+Error(subject/time.points))) > test.summary Error: subject Df...
2011 Dec 11
6
multiple comparison of interaction of ANCOVA
...5.55 2010 C"), header = TRUE) > closeAllConnections() The experiments is designed without replication, thus I have to use ANCOVA or linear mixed effect model to analyze the data. In the model, variable year is coded as a continuous variable, and Trt is factor variable. > mydata.aov <- aov(y~Trt*year, mydata) > anova(mydata.aov) Analysis of Variance Table Response: y Df Sum Sq Mean Sq F value Pr(>F) Trt 2 140.106 70.053 197.9581 3.639e-08 *** year 1 0.610 0.610 1.7246 0.221600 Trt:year 2 8.804 4.402 12.4387 0.002567 ** Re...
2007 Oct 07
1
Question about aov
Hello R gurus, I am a beginner with R. I am doing an ANCOVA analysis using ''aov,'' and need some help understanding how ''aov'' works. I have a dataset (taken from http://faculty.vassar.edu/lowry/ch17pt2.html) looking at hypnotic induction. The variable ''X'' is a measure of how susceptible the subject is to being hypno...
2012 Oct 08
2
aov() usage
Hi R-listers, I am wondering if the function aov() in plyr is appropriate for two different types of tests: 1) > summary(aov(EDI ~ VegIndex, data=data.to.analyze)) AND 2) > summary(aov(HSuccess ~ VegIndex + Aeventexhumed + VegIndex:Aeventexhumed, data=data.to.analyze)) the later inclusive of an interaction of the two explanatory variabl...
2002 Dec 09
4
Problem with differences between S+ and R in parsing output tables with $
...t doesn''t seem to retrieve the appropriate number from a table. Note that some of the cosmetic differences in the two tables have to be dealt with by the parser. Any ideas what''s happening? REX # Begin R ------------------------------------------------------------- # > summary(aov(model)) Df Sum Sq Mean Sq F value Pr(>F) fa 1 11.1 11.1 0.9327 0.3345 Residuals 698 8279.3 11.9 # R: ... trying to parse the table gives a NULL for the probability of F... > (summary(aov(model))$"Pr(>F)")[1] NULL # End R -----...
2008 Dec 16
3
model.tables error from aov
...Mean :13.40 18 : 3 3rd Qu.:16.00 2 : 3 Max. :59.00 (Other):40 Note that the TrainErrs column is the only numeric column, and I forced everything else to be a factor. (Is that correct?) I then do the following: aov.errs.ae <- aov(TrainErrs ~ (idio*Type) + Error(Subject/Type) + (idio), learnDat.ae) So, idio is between-subjects and Type is within-subjects. This is based on examples I''ve found elsewhere. summary(aov.errs.ae) This seems to work fine: Error: Subject Df Sum Sq Mean Sq...
2008 Mar 10
4
question for aov and kruskal
Hi R users! I have the following problem: how appropriate is my aov model under the violation of anova assumptions? Example: a<-c(1,1,1,1,1,1,1,1,1,1,2,2,2,3,3,3,3,3,3,3) b<-c(101,1010,200,300,400, 202, 121, 234, 55,555,66,76,88,34,239, 30, 40, 50,50,60) z<-data.frame(a, b) fligner.test(z$b, factor(z$a)) aov(z$b~factor(z$a))->ll TukeyHSD(ll) Now from...
2006 Nov 03
6
ANOVA in Randomized-complete blocks design
...quite confident how to represent this model in R, see below) The ANOVA table from S&R looks like this: MSB series 3 0.021 0.007 10.23 ** MSA genotypes 2 0.010 0.005 6.97 * MSE error 6 0.004 0.001 In R, I am using the following model (is this correct?) aov.ob = aov( genotype ~ genotype + series ) However, my results are Df Sum Sq Mean Sq F value Pr(>F) series 3 0.0135867 0.0045289 6.6360 0.02469 * genotype 2 0.0056732 0.0028366 4.1563 0.07367 . Residuals 6 0.0040948 0.0006825 What am I doing wrong? Regards, Jan...
2008 Mar 15
2
Anova
Hi all, I apologize for what might be a silly question. I am interested in doing a one way anova. This is not too hard in and of itself, either with anova, aov or oneway.test . However, I need to 1) get pvalues, 2) do a posthoc analysis with Tukey HSD, 3) and have (sometimes) an unbalanced design. I just can''t seem to put all the pieces together. Any suggestions? Thanks in advance, Dan. -- Daniel C. Jupiter, Ph.D. Postdoctoral Research Ass...
2004 Jan 16
2
error message in plot(aov-object) -- repost
Hi all, I posted this question several days ago, but did not get any answer until now. Since I still have no clue about the source of this error message, I repost a description of the problem including some code: A student at our institute fitted an aov model, and got the following error message: > plot(p.aov) Hit <Return> to see next plot: Hit <Return> to see next plot: Error in plot.window(xlim, ylim, log, asp, ...) : need finite ylim values The second plot was not produced. I then tried to produced the plot manuall...
2000 Jul 05
1
Tukey.aov with split-plot designs
I am using R 1.1 with Redhat 6.2 and RW 1.001 with Win98 (the upkey doesn't work on my IBM either as has been previously reported by others). The function aov doesn't return either the residuals or the residual degrees of freedom for split-plot designs. If you use the following code from Baron and Li's "Notes on the use of R for psycology experiments and questionnaires" data <- c(30,14,24,38,26,28,18,20,34,28,16,10,18,20,14,34,22,...
2008 Sep 13
2
moving from aov() to lmer()
Hello, I''ve used this command to analyse changes in brain volume: mod1<-aov(Volume~Sex*Lobe*Tissue+Error(Subject/(Lobe*Tissue)),data.vslt) I''m comparing males/females. For every subject I have 8 volume measurements (4 different brain lobes and 2 different tissues (grey/white matter)). As aov() provides only type I anovas, I would like to use lmer() w...