Sparse Matrix Representation With NAs Not Explicitly Stored
Coerce from and to a
sparse matrix representation where
NAs are not explicitly stored.
- a matrix (for
dropNA()). A sparse matrix (for
The representation is based on
the sparse dgCMatrix in Matrix but instead of zeros,
NAs are dropped.
Note: Be careful when working with matrix operations (multiplication, addition, etc.) since these will use the dgCMatrix superclass which assumes that all dropped values are zero and not NA! This means that the operations might remove zeros or add to NAs incorrectly.
- Returns a dgCMatrix or a matrix, respectively.
dgCMatrix in Matrix.
m <- matrix(sample(c(NA,0:5),50, replace=TRUE, prob=c(.5,rep(.5/6,6))), nrow=5, ncol=10, dimnames = list(users=paste('u', 1:5, sep=''), items=paste('i', 1:10, sep=''))) m ## drop all NAs in the representation sparse <- dropNA(m) sparse ## convert back to matrix dropNA2matrix(sparse)