Thanks Steve, Now it is a bit clear to me, thanks very much.
----- Original Message ----- From: "S Ellison" <[EMAIL PROTECTED]> To: <[EMAIL PROTECTED]>; "sun" <[EMAIL PROTECTED]> Sent: Friday, October 12, 2007 12:59 PM Subject: Re: [R] how to generate and evaluate a design using Algdesign > If you do something like length(coef(lm(y~.+v3:v4 + v5:v6, data=dat))) > to get a quick empirical estimate of required number of coefficients, > you will find that you have 35 coefficients, so 32 observations cannot > provide a solution at all. And indeed, nTrials=35 is the first size at > which optFederov even tries to find a design. > > After that,many possible trial designs will be singular because (I > think) most subsets of the data will miss out support points for the > design. You need a lot of repeats to find a design at all with so few > points, or optfederov won't find a viable design at all. > > If you're prepared to wait a while, run with at least nTrials=45 with > plenty of repeats and you have a chance of something useful, though the > efficiency (judged by Ge) looked pretty poor. > > Steve E >>>> "sun" <[EMAIL PROTECTED]> 10/10/2007 14:59:59 >>> > Hi, > > I have some problems when using AlgDesign->optFederov() generating > designs. > > I have 6 variables, all factors. 3^2 and 4^4, I want to have a design > that > can take care of main effects and two interactions within 2 pair of > variables v3-v4 and v5-v6, the following is the code > > ################ > require(AlgDesign) > set.seed(1) > levels = c(v1=3,v2=3, v3=4,v4=4,v5=4,v6=4) > > dat<-gen.factorial(levels,center=FALSE,varNames=names(levels),factors= > c(1,2,3,4,5,6)) > > model = ~.+v3:v4+v5:v6 > > optDgn<-optFederov(model,dat,nRepeat=5,nTrials = 32,criterion = "D", > approximate = F) > > ---------------------------- > this lead to a error msg " nTrials must be greater than or equal to > the > number of columns in expanded X" . I thought I do not have that many > columns. if I change approximate to T, this error has gone. > > if I remove nTrials argument in function call: >> optDgn<-optFederov(~.+v3:v4+v5:v6,dat,nRepeat=5,criterion = >> "D",approximate = F) > I got a error : "Singular design." > > what would be the cause and what is the sullotion? > > another question is, how do I measure or evaluate a design to see if it > is > able to handle which effects(main effects/which intercations)? I got > some > other designs generated by other packages, so I 'd like to check their > > characteristics. > > Thanks in advance, > > Sun > > ______________________________________________ > R-help@r-project.org mailing list ______________________________________________ R-help@r-project.org 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.
