How do I set the replaced value in a sparse matrix to NA rather than 0?

Question

I would like to use sparse matrices for an analysis. Each cell in the sparse matrix comprises one value from the set {0,1,NA}. NA here represents a missing value.

For example, I can use the following code to create a sparse matrix:

    library(Matrix); 
    toy <- Matrix(c(0,1,NA), nrow=3, ncol=3, sparse = TRUE)

and I get the following output:

.  .  .
1  1  1
NA NA NA

Is it possible to use the Matrix function to create a function in which the datapoints 'left out' of the matrix are the NA values rather than 0? Are there other functions that I could use?

Therefore, from my example, my desired output is:

0 0 0
1 1 1
. . .

I have explored help pages and websites but I haven't found the answer. I believe I need to set the 'replValue'.

Answer 1

There are two separate questions, actually. The first one is how to display zeroes. It is easy to solve by looking for the exact method that is used after dispatch:

Matrix::printSpMatrix(toy, zero.print="0")

[1,]  0  0  0
[2,]  1  1  1
[3,] NA NA NA

The second question is whether the NA output can be suppressed with some other character. Well, it is not directly possible: there is no suitable parameter for that.

However, modifying the source is always an option. Beware: this is a hack, which may lead to unforseen consequences!

toy_print <- function (x, digits = NULL, maxp = getOption("max.print"), cld = getClassDef(class(x)), 
                       zero.print = ".", col.names, note.dropping.colnames = TRUE, 
                       col.trailer = "", align = c("fancy", "right")) 
{
    stopifnot(extends(cld, "sparseMatrix"))
    x.orig <- x
    cx <- formatSpMatrix(x, digits = digits, maxp = maxp, cld = cld, 
                         zero.print = zero.print, col.names = col.names, note.dropping.colnames = note.dropping.colnames, 
                         align = align)
    if (col.trailer != "") 
        cx <- cbind(cx, col.trailer, deparse.level = 0)
    # here's the NA hack
    cx[cx=="NA"] <- "."
    print(cx, quote = FALSE, right = TRUE, max = maxp)
    invisible(x.orig)
}

toy_print(toy, zero.print="0")

[1,]  0  0  0
[2,]  1  1  1
[3,]  .  .  .