search for: xpnd

Dear R-list members, Just wondering if there is any way to compute the duplication matrix in R. I tried to search for it but only found functions "xpnd" and "vech". Basically for a symmetric n by n matrix A, the duplication matrix D_n is a matrix of dimension n^2 by n(n+1)/2 such that D_n vech(A)= c(A), where c(A) just vectorizes A. The duplication matrix is defined on page 49 of the book "Matrix differential calculus with...

...(lmexp, data=xd) # NOTE: THE STEP() TAKES FOREVER IN R # tmpzx2 <-lm(lmexpall,data=xd) # tmpzxall <- step(tmpzx2, trace=0) cat ("Done building model", "\n") # Get predictions xp <- predict(tmpzx,se.fit=T,interval=c("confidence")) xpnd <- xp xpndfit.df <- as.data.frame(xpnd$fit) xpnd.o <- data.frame(act=get(resp),fit.act=xp$fit) mapres.opact <- data.frame(act=get(resp)) mapres.opprd <- data.frame(fit.act=xp$fit) write.table(xpnd.o,"lmtst.dat",quote=F,row.names=F) mapres.op <- da...

Let say i have a square matrix and applied the 'vech' operator to stack the lower triangular elements into a vector: > Mat <- matrix(1:25, 5) > Mat ? ? ?[,1] [,2] [,3] [,4] [,5] [1,] ? ?1 ? ?6 ? 11 ? 16 ? 21 [2,] ? ?2 ? ?7 ? 12 ? 17 ? 22 [3,] ? ?3 ? ?8 ? 13 ? 18 ? 23 [4,] ? ?4 ? ?9 ? 14 ? 19 ? 24 [5,] ? ?5 ? 10 ? 15 ? 20 ? 25 > Mat[lower.tri(Mat)] ?[1] ?2 ?3 ?4 ?5 ?8 ?9 10 14

# I've tried to make this easy to paste into R, though it's probably so simple you won't need to. # I have some data (there are many more variables, but this is a reasonable approximation of it) # here's a fabricated data frame that is similar in form to mine: my.df <- data.frame(replicate(10, round(rnorm(100, mean=3.5, sd=1)))) var.list <- c("dv1",

Hello I have data like this x1 x2 x3 x4 x5 I want to create a matrix similar to a correlation matrix, but with the difference between the two values, like this x1 x2 x3 x4 x5 x1 x2-x1 x3-x1 x4-x1 x5-x1 x2 x3-x2 x4-x2 x5-x2 x3 x4-x3 x5-x3 x4 x5-x4 x5 Then I