The simplest way to create a matrix is to type it in at the command line:
> m = [ 1, 2, 3; 4, 5, 6; 7, 8, 9 ] m = 1 2 3 4 5 6 7 8 9
In this context the `[ ]
' signal RLaB that a matrix should
be created. The inputs (or arguments) for matrix creation are
whatever is inside the `[ ]
'. The rows of the matrix are
delimited with `;
' and the elements of each row are
delimited with `,
'.
Users can use most any expression when creating matrix elements.
Other matrices, function evaluations, and arithmetic operations are
allowed when creating matrix elements. In the next example, we will
create a direction cosine matrix using the built-in trigonometric
functions within the `[ ]
'.
> a = 45*(2*pi)/360 a = 0.785 > A = [ cos(a), sin(a); -sin(a), cos(a) ] A = 0.707 0.707 -0.707 0.707
Matrices can also be read from disk-files. The functions
read
, readb
and readm
can read matrix values
from a file. The read
function uses a special ASCII text
file format, and is capable of reading not only matrices, but
strings, and lists as well. Since the file can contain many data
objects, and their variable names, read
is used like:
> read ( "file.dat" );
The variables are read from file.dat
and installed in the
global-symbol-table.
The readb
function works like read
, except it reads
binary files for greater efficiency. The binary files created with
writeb
are portable across computers that use IEEE floating
point format.
The readm
function reads a text file that contains
white-space separated columns of numbers. readm
is most
often used to read in data created by other programs. Since
readm
is only capable of reading in one matrix per file, and
no variable name information is available, readm
is used
like:
> a = read ( "a.dat" );