An S4 class to represent a stratigraphic matrix.

## Details

A stratigraphic matrix represents directed relationships between stratigraphic units. A stratigraphic matrix is an adjacency matrix (a non symmetric square matrix with zeros on its main diagonal), suitable to build a directed acyclic graph (DAG).

## Access

In the code snippets below, x is a *Matrix object.

length(x)

Returns the length of x.

dim(x)

Returns the dimension of x.

nrow(x)

Returns the number of rows present in x.

ncol(x)

Returns the number of columns present in x.

dimnames(x), dimnames(x) <- value

Retrieves or sets the row dimnames of x according to value.

rownames(x), rownames(x) <- value

Retrieves or sets the row names of x according to value.

colnames(x), colnames(x) <- value

Retrieves or sets the column names of x according to value.

## Subset

In the code snippets below, x is a *Matrix object.

x[i, j, ..., drop]

Extracts elements selected by subscripts i and j. Indices are numeric or character vectors or empty (missing) or NULL. Numeric values are coerced to integer as by as.integer (and hence truncated towards zero). Character vectors will be matched to the dimnames of the object. An empty index (a comma separated blank) indicates that all entries in that dimension are selected. Returns an object of the same class as x.

x[[i]]

Extracts a single element selected by subscript i.

as_stratigraphy

Other matrix: AbundanceMatrix-class, CountMatrix-class, DataMatrix-class, GenericMatrix-class, IncidenceMatrix-class, OccurrenceMatrix-class, SimilarityMatrix-class, coerce()

N. Frerebeau

## Examples

# Principles of Archaeological Stratigraphy, fig. 12
harris <- matrix(
data = c(2, 1,
3, 1,
4, 1,
5, 2,
5, 3,
5, 4,
6, 5,
7, 1,
7, 6,
8, 1,
8, 6,
9, 7,
9, 8),
ncol = 2,
byrow = TRUE,
dimnames = list(NULL, c("lower", "upper"))
)

strati <- as_stratigraphy(harris)