General Folding of Matrix
General folding of a matrix into a Tensor. This is designed to be the inverse function to unfold-methods, with the same ordering of the indices. This amounts to following: if we were to unfold a Tensor using a set of row_idx and col_idx, then we can fold the resulting matrix back into the original Tensor using the same row_idx and col_idx.
fold(mat, row_idx = NULL, col_idx = NULL, modes = NULL)
mat |
matrix to be folded into a Tensor |
row_idx |
the indices of the modes that are mapped onto the row space |
col_idx |
the indices of the modes that are mapped onto the column space |
modes |
the modes of the output Tensor |
This function uses aperm as the primary workhorse.
Tensor object with modes given by modes
T. Kolda, B. Bader, "Tensor decomposition and applications". SIAM Applied Mathematics and Applications 2009.
tnsr <- new("Tensor",3L,c(3L,4L,5L),data=runif(60))
matT3<-unfold(tnsr,row_idx=2,col_idx=c(3,1))
identical(fold(matT3,row_idx=2,col_idx=c(3,1),modes=c(3,4,5)),tnsr)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.