search for: unbalanced

Displaying 20 results from an estimated 506 matches for "unbalanced".

2008 Feb 28
4
unbalanced one-way ANOVA
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 samp...
2007 Apr 03
2
Coding for contrasts in unbalanced designs
Dear list members, I want to use a GLM with an unbalanced factor and continuous variables. My factor F has 12 unbalanced levels: F=as.factor(c('A','B','C','C','C','C','D','D','D','D','D','D','E','E','E','E','E','E'...
2012 Oct 29
2
Two-way Random Effects with unbalanced data
...d* layout, y_ijk = mu + a_i + b_j + eps_ijk, i=1,...,R, j=1,...,C, k=1,...,K_ij. I am interested first of all in estimates for the variance components, sigsq_a, sigsq_b and sigsq_error. In the balanced case, there are simple (MM, MLE) estimates for these; In the unbalanced setup, this is much more complicated because orthogonality relations no longer exist between "row space" and "column space". Since the covariance structure between the cell means y_{ij.} is much more complicated than in the one-way (unbalanced) case, trying to manually obtain ML...
2011 Apr 03
2
Unbalanced Anova: What is the best approach?
I have a three-way unbalanced ANOVA that I need to calculate (fixed effects plus interactions, no random effects). But word has it that aov() is good only for balanced designs. I have seen a number of different recommendations for working with unbalanced designs, but they seem to differ widely (car, nlme, lme4, etc.). So I woul...
2009 Jun 23
1
nlme package - unbalanced data and Croissant (2008)
Dear listserv members, In Croissant (2008) “Panel Data Econometrics in R: The plm Package” the authors seem to indicate that the nlme package for R cannot correctly handle unbalanced panel data: “Moreover, economic panel datasets often happen to be unbalanced (i.e., they have a different number of observations between groups), which case needs some adaptation to the methods and is not compatible with those in nlme” (pg. 2, Croissant 2008). However in Pinhiero and Bates (2000,...
2011 Jan 08
1
Anova with repeated measures for unbalanced design
Dear all, I need an help because I am really not able to find over internet a good example in R to analyze an unbalanced table with Anova with repeated measures. For unbalanced table I mean that the questions are not answered all by the same number of subjects. For a balanced case I would use the command aov1 = aov(response ~ stimulus*condition + Error(subject/(stimulus*condition)), data=scrd) Does the same cod...
2011 May 21
2
unbalanced anova with subsampling (Type III SS)
Hello R-users, I am trying to obtain Type III SS for an ANOVA with subsampling. My design is slightly unbalanced with either 3 or 4 subsamples per replicate. The basic aov model would be: fit <- aov(y~x+Error(subsample)) But this gives Type I SS and not Type III. But, using the drop() option: drop1(fit, test="F") I get an error message: "Error in UseMethod("extractAIC") : no ap...
2004 Dec 01
2
unbalanced design
Hi all, I'm new to R and have the following problem: I have a 2 factor design (a has 2 levels, b has 3 levels). I have an object kidney.aov which is an aov(y ~ a*b), and when I ask for model.tables(kidney.avo, se=T) I get the following message along with the table of effects: Design is unbalanced - use se.contrast() for se's but the design is NOT unbalanced... each fator level combination has the same n I' d appreciate any help. Thanks.
2011 Feb 27
1
two-way unbalanced ANOVA
Hello Everyone, *Question: *How do you calculate the sum of squares for a two-way _unbalanced_ ANOVA? *What I have done:* I have found many useful tutorials online for running a balanced two-way ANOVA but I haven't had much luck for running a unbalanced two-way ANOVA. From what I have read, the trouble with running an unbalanced two-way ANOVA, is that things get tricky when calculat...
2002 Mar 08
3
Unbalanced ANOVA in R?
Hi all I'm trying to complete a textbook example originally designed for SPSS in R, and I therefore need to find out how to compute an unbalanced ANOVA in R. I did a search on the mailinglist archives an found a post by Prof. Ripley saying one should use the lme function for (among other things) unbalanced ANOVAs, but I have not been able to use this object. My code gives me an error.. Why is that ? > aov(lme(DELAY ~ DOSE + TRIALS,data=...
2004 Jun 28
1
unbalanced design for anova with low number of replicates
Hello, I'm wondering what's the best way to analyse an unbalanced design with a low number of replicates. I'm not a statistician, and I'm looking for some direction for this problem. I've a 2 factor design: Factor batch with 3 levels, and factor dose within each batch with 5 levels. Dose level 1 in batch one is replicated 4 times, level 3 is replica...
2012 Jun 12
1
Unbalanced Design Power Analysis
I have an unbalanced design I would like to run a power analysis on. What I have been able to find has pointed me to using the pwr.f2.test function as described below. My problem is that I don't know how to appropriately define the numerator and demoninator df. If someone can help here is some more info about my d...
2011 Mar 08
1
lags for unbalanced panel data
Hello, I was wondering if there was an easy way to calculate the rate of change in a variable for an unbalanced panel data set. Below is a detailed description in R of what I am asking. Thank you. Geoff #Suppose I have the following unbalanced panel data; Person <- c(rep('Frank',5), rep('Tony',4), rep('Edward',4)); Year <- c(2005,2006,2007,2008,2009,2005,2006,2008,2009,2006...
2011 Apr 26
1
logistic regression: wls and unbalanced samples
Greetings from Rio de Janeiro, Brazil. I am looking for advice / references on binary logistic regression with weighted least squares (using lrm & weights), on the following context: 1) unbalanced sample (n0=10000, n1=700); 2) sampling weights used to rebalance the sample (w0=1, w1=14.29); e 3) after modelling, adjust the intercept in order to reflect the expected % of 1?s in the population (e.g., circa 7%, as opposed to 50%). I have identified references that deal with the last point, but...
2012 Aug 14
2
anova in unbalanced data
Hi all, Say I have the following data: a<-data.frame(col1=c(rep("a",5),rep("b",7)),col2=runif(12)) a_aov<-aov(a$col2~a$col1) summary(aov) Note that there are 5 observations for a and 7 for b, thus is unbalanced. What would be the correct way of doing anova for this set? Thanks, Sachin [[alternative HTML version deleted]]
2001 Mar 10
3
Problem With Model.Tables Function
...15.333 trtmnts 1 2 3 10.50 13.75 19.00 Entering the data again and dropping treatment 2, block3 and treatment 3, block 4, we have: > blocks2<-factor(c(1,2,3,4,1,2,4,1,2,3)) > trtmts2<-factor(c(1,1,1,1,2,2,2,3,3,3,)) > data2<-c(10,12,9,11,13,15,16,18,22,17) > unbalanced<-aov(data2~blocks2+trtmts2) > summary(unbalanced) Df Sum Sq Mean Sq F value Pr(>F) blocks2 3 18.267 6.089 7.4341 0.0410993 * trtmts2 2 126.557 63.279 77.2587 0.0006367 *** Residuals 4 3.276 0.819 --- Signif. codes: 0 `***' 0.001 `**' 0.01...
2006 Mar 30
2
Unbalanced Manova
Dear all, I need to do a Manova but I have an unbalanced design. I have morphological measurements similar to the iris dataset, but I don't have the same number of measurements for all species. Does anyone know a procedure to do Manova with this kind of input in R? Thank you very much, Naiara. -------------------------------------------- Naiara S....
2011 Feb 07
2
Unbalanced Mixed Linear Models With Nested Stratum
...easuring the subjects' pupils. There are many measurements, all of which must be analysed in a similar fashion; so if I get the analysis right for one of them, I've got them all. For simplicity, let us call any measurement we may be interested as "response". The study design is an unbalanced latin square, with 5 periods, 5 treatments and 6 subjects. Each subject has two measurements: left and right eyes. The model is as follows, with ":" denoting interaction... Fixed Effects = (Subject + Period + Dose):Eye Random Effects = Subject:Period + Subject:Period:Eye My main questio...
2007 Sep 14
2
unbalanced effects in aov
Hi, I have been having some trouble using aov to do an anova, probably because I'm not understanding how to use this function correctly. For some reason it always tells me that "Estimated effects may be unbalanced", though I'm not sure what this means. Is the formula I am using written incorrectly? Below is the code I am using along with the data: > my.data response species sex line replicate plate 1 -7.092854e-03 1 1 1 1 1 2 -8.663481e-04 1 2 1...
2004 Mar 09
2
SVM unbalanced classes
Hi! I am using R 1.8.1 and the svm of the e1071 package for classification. The problem is that I have unbalanced classes e.g. the first one is much bigger than the second one and therfore the svm is biased to the first class. If I manually adjust the class size the bias disappears. The question is then how to include this unequal class distribution to the svm (e.g. via wheights or costs)? Yours, Frank -- Fr...