```
# NOT RUN {
## A random sparse matrix :
set.seed(7)
m <- matrix(0, 5, 5)
m[sample(length(m), size = 14)] <- rep(1:9, length=14)
(mm <- as(m, "CsparseMatrix"))
tril(mm) # lower triangle
tril(mm, -1) # strict lower triangle
triu(mm, 1) # strict upper triangle
band(mm, -1, 2) # general band
(m5 <- Matrix(rnorm(25), nc = 5))
tril(m5) # lower triangle
tril(m5, -1) # strict lower triangle
triu(m5, 1) # strict upper triangle
band(m5, -1, 2) # general band
(m65 <- Matrix(rnorm(30), nc = 5)) # not square
triu(m65) # result in not dtrMatrix unless square
(sm5 <- crossprod(m65)) # symmetric
band(sm5, -1, 1)# symmetric band preserves symmetry property
as(band(sm5, -1, 1), "sparseMatrix")# often preferable
# }
# NOT RUN {
<!-- %% -->
# }
```

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