Octave supports a number of different array and matrix classes, the majority of which are based on the Array class. The exception is the sparse matrix types discussed separately below. There are three basic matrix types
Matrix
ComplexMatrix
BoolMatrix
These are the basic two-dimensional matrix types of Octave. In addition there are a number of multi-dimensional array types including
NDArray
ComplexNDarray
boolNDArray
int8NDArray
int16NDArray
int32NDArray
int64NDArray
uint8NDArray
uint16NDArray
uint32NDArray
uint64NDArray
There are several basic ways of constructing matrices or
multi-dimensional arrays. Using the class Matrix
as an example
one can
Matrix a;
This can be used for all matrix and array types.
size
. For example:
dim_vector dv (2, 3); // 2 rows, 3 columns Matrix a (dv);
This can be used on all matrix and array types.
Matrix a (2, 2)
However, this constructor can only be used with matrix types.
These types all share a number of basic methods and operators. Many bear a resemblance to functions that exist in the interpreter. A selection of useful methods include
The
()
operator orelem
method allow the values of the matrix or array to be read or set. These can take a single argument, which is of typeoctave_idx_type
, that is the index into the matrix or array. Additionally, the matrix type allows two argument versions of the()
operator and elem method, giving the row and column index of the value to obtain or set.
Note that these functions do significant error checking and so in some circumstances the user might prefer to access the data of the array or matrix directly through the fortran_vec method discussed below.
The dimensions of the matrix or array in value of type dim_vector.
The number of dimensions of the matrix or array. Matrices are 2-D, but arrays can be N-dimensional.
A method taking either an argument of type
dim_vector
, or in the case of a matrix two arguments of typeoctave_idx_type
defining the number of rows and columns in the matrix.
This method returns a pointer to the underlying data of the matrix or array so that it can be manipulated directly, either within Octave or by an external library.
Operators such an +
, -
, or *
can be used on the
majority of the matrix and array types. In addition there are a number of
methods that are of interest only for matrices such as transpose
,
hermitian
, solve
, etc.
The typical way to extract a matrix or array from the input arguments of
DEFUN_DLD
function is as follows
#include <octave/oct.h> DEFUN_DLD (addtwomatrices, args, , "Add A to B") { int nargin = args.length (); if (nargin != 2) print_usage (); else { NDArray A = args(0).array_value (); NDArray B = args(1).array_value (); if (! error_state) return octave_value (A + B); } return octave_value_list (); }
To avoid segmentation faults causing Octave to abort this function
explicitly checks that there are sufficient arguments available before
accessing these arguments. It then obtains two multi-dimensional arrays
of type NDArray
and adds these together. Note that the array_value
method is called without using the is_matrix_type
type, and instead the
error_state is checked before returning A + B
. The reason to
prefer this is that the arguments might be a type that is not an
NDArray
, but it would make sense to convert it to one. The
array_value
method allows this conversion to be performed
transparently if possible, and sets error_state
if it is not.
A + B
, operating on two NDArray
's returns an
NDArray
, which is cast to an octave_value
on the return
from the function. An example of the use of this demonstration function is
addtwomatrices (ones (2, 2), eye (2, 2)) ⇒ 2 1 1 2
A list of the basic Matrix
and Array
types, the methods to
extract these from an octave_value
, and the associated header file is
listed below.
Type | Function | Source Code
|
---|---|---|
RowVector | row_vector_value | dRowVector.h
|
ComplexRowVector | complex_row_vector_value | CRowVector.h
|
ColumnVector | column_vector_value | dColVector.h
|
ComplexColumnVector | complex_column_vector_value | CColVector.h
|
Matrix | matrix_value | dMatrix.h
|
ComplexMatrix | complex_matrix_value | CMatrix.h
|
boolMatrix | bool_matrix_value | boolMatrix.h
|
charMatrix | char_matrix_value | chMatrix.h
|
NDArray | array_value | dNDArray.h
|
ComplexNDArray | complex_array_value | CNDArray.h
|
boolNDArray | bool_array_value | boolNDArray.h
|
charNDArray | char_array_value | charNDArray.h
|
int8NDArray | int8_array_value | int8NDArray.h
|
int16NDArray | int16_array_value | int16NDArray.h
|
int32NDArray | int32_array_value | int32NDArray.h
|
int64NDArray | int64_array_value | int64NDArray.h
|
uint8NDArray | uint8_array_value | uint8NDArray.h
|
uint16NDArray | uint16_array_value | uint16NDArray.h
|
uint32NDArray | uint32_array_value | uint32NDArray.h
|
uint64NDArray | uint64_array_value | uint64NDArray.h
|