search for: mydv

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2011 Nov 10
3
optim seems to be finding a local minimum
...rns a data frame column IV_transf: transformIV = function(.alpha,.beta) { IV_transf <- as.data.frame(1 - (1/exp((IV/.beta)^.alpha))) return(IV_transf) } ### Function "mysum" calculates the sum of absolute residuals after a regression with a single predictor: mysum<- function(myIV,myDV){ regr<-lm(myDV[[1]] ~ 0 + myIV[[1]]) mysum<-sum(abs(regr$resid)) return(mysum) } ### Function to be optimized; ### param is a vector of 2 values (.alpha and .beta) myfunc <- function(param){ myalpha<-param[1] mybeta<-param[2] IVtransf<-transformIV(myalpha, mybeta)...
2009 Mar 03
1
repeated measures anova, sphericity, epsilon, etc
...ated measures anova. This time around teaching it, we are using R for all of our computations. We are starting by covering the univariate approach to repeated measures anova. Doing a basic repeated measures anova (univariate approach) using aov() seems straightforward (e.g.: +> myModel<-aov(myDV~myFactor+Error(Subjects/myFactor),data=myData) +> summary(myModel) Where I am currently stuck is how best to deal with the issue of the assumption of homogeneity of treatment differences (in other words, the sphericity assumption) - both how to test it in R and how to compute corrected df for t...