R Under development (unstable) (2025-08-17 r88631 ucrt) -- "Unsuffered Consequences"
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> ## any sparse matrix format that inherits from dMatrix should work
> library(sparsesvd)
> library(Matrix)
> 
> M <- rbind(
+   c(20, 10, 15,  0,  2),
+   c(10,  5,  8,  1,  0),
+   c( 0,  1,  2,  6,  3),
+   c( 1,  0,  0, 10,  5))
> 
> M1 <- Matrix(M, sparse=TRUE)          # standard format (column-compressed)
> M1 <- as(M1, "CsparseMatrix")
> stopifnot(is(M1, "dgCMatrix"))
> res1 <- sparsesvd(M1)
> 
> M2 <- Matrix(M, sparse=FALSE)         # dense matrix
> stopifnot(is(M2, "dgeMatrix"))
> res2 <- sparsesvd(M2)
> 
> M3 <- Matrix(M, sparse=TRUE)          # triplet format
> M3 <- as(M3, "TsparseMatrix")
> stopifnot(is(M3, "dgTMatrix"))
> res3 <- sparsesvd(M3)
> 
> M4 <- Matrix(M, sparse=TRUE)          # row-compressed
> M4 <- as(M4, "RsparseMatrix")
> stopifnot(is(M4, "dgRMatrix"))
> res4 <- sparsesvd(M4)
> ## TODO -- row-compressed form cannot be converted to dgCMatrix
> 
> ## check that eigenvalues are the same
> stopifnot(all.equal(res1$d, res2$d, tolerance=1e-12))
> stopifnot(all.equal(res1$d, res3$d, tolerance=1e-12))
> stopifnot(all.equal(res1$d, res4$d, tolerance=1e-12))
> 
> ## special classes for symmetric matrices
> A1 <- crossprod(M1)
> A1 <- as(A1, "CsparseMatrix")
> stopifnot(is(A1, "dsCMatrix"))
> res1a <- sparsesvd(A1)
> 
> A2 <- crossprod(M2)
> stopifnot(is(A2, "dpoMatrix")) # dense positive-semidefinite symmetric matrix
> res2a <- sparsesvd(A2)
> ## -- fails
> 
> A3 <- as(A1, "TsparseMatrix")
> stopifnot(is(A3, "dsTMatrix"))
> res3a <- sparsesvd(A3)
> ## -- symmetric matrix can only be converted if already in row-compressed form
> 
> A4 <- as(A1, "RsparseMatrix")
> stopifnot(is(A4, "dsRMatrix"))
> res4a <- sparsesvd(A4)
> ## -- fails 
> 
> ## check that eigenvalues are the same and consistent with M
> stopifnot(all.equal(res1a$d, (res1$d)^2, tolerance=1e-12))
> stopifnot(all.equal(res1a$d, res2a$d, tolerance=1e-12))
> stopifnot(all.equal(res1a$d, res3a$d, tolerance=1e-12))
> stopifnot(all.equal(res1a$d, res4a$d, tolerance=1e-12))
> 
> proc.time()
   user  system elapsed 
   0.96    0.10    1.06