[R] Matrix multiplication - code problem

Hi listers, I am having some trouble in a matrix multiplication... I have already checked some posts, but I didn't find my problem... I have the following code... But I am not getting the right multiplication... I checked the dimension and they are fine... id_y <- array(1:10,dim=c(2,1,5)) id_yt<-

Re: [R] Matrix multiplication - code problem

MarcioRibeiro wrote: > > Hi listers, > I am having some trouble in a matrix multiplication... > I have already checked some posts, but I didn't find my problem... > I have the following code... > But I am not getting the right multiplication... > I checked the dimension and they are fine... >

Re: [R] Matrix multiplication - code problem

I think your problem is with R's behavior of dropping array indices when dim==1. Simulating that > m1 <- matrix(1:2,nrow=2) > m2 <- matrix(1:2,ncol=2) > m1 %*% m2 [,1] [,2] [1,]12 [2,]24 > m1[,] %*% m2[,] [,1] [1,]5 [1,]5 > m1[,,drop=FALSE] %*% m2[,,drop=

Re: [R] Matrix multiplication - code problem

Hi again... I will get an array with 5 matrix 2x2, with dimension 2x2x5 This code below works fine... And I am applying the same procedure... The problem might be when I do the permutation of the array, but I checked the dimension and its all right... array1 <- array(1:30,dim=c(3,2,5)) array2 <-

Re: [R] Matrix multiplication - code problem

MarcioRibeiro wrote: Hi listers, I am having some trouble in a matrix multiplication... I have already checked some posts, but I didn't find my problem... I have the following code... But I am not getting the right multiplication... I checked the dimension and they are fine... id_y <- array(1:

Re: [R] Matrix multiplication - code problem

Hi again, I understood what you guys explained... But, there isn't a way to do a multiplication of matrix with a FOR command or otherelse where one o my dimension is ONE... Well, as my data file is small, I did the procedure at the excel... But, this is not the good procedure... Thanks, Marcio U

Re: [R] Matrix multiplication - code problem

You need to put in calls to 'as.matrix'. It's a bit tricky though -- what you want depends on whether it is the first or second subscript that has length 1. as.matrix(id_y[,,i]) if the second dimension has length 1. t(as.matrix(id_y[,,i])) if the first dimension has length 1. Patrick Burns

Re: [R] Matrix multiplication - code problem

I think this works in general, although it's a little bit clunky: id_y <- array(1:10,dim=c(2,1,5)) id_yt <- aperm(id_y,c(2,1,3)) m_id <- array(dim=c(dim(id_y)[1],dim(id_y)[1],dim(id_y)[3])) for (i in 1:dim(id_y)[3]){ m1 <- array(id_y[,,i],dim=dim(id_y)[1:2]) m2 <- array(id_yt[,,i],dim=di