Node:Special Utility Matrices, Next:Famous Matrices, Previous:Rearranging Matrices, Up:Matrix Manipulation
eye (x) | Built-in Function |
eye (n, m) | Built-in Function |
eye (..., class) | Built-in Function |
Return an identity matrix. If invoked with a single scalar argument,
eye returns a square matrix with the dimension specified. If you
supply two scalar arguments, eye takes them to be the number of
rows and columns. If given a vector with two elements, eye uses
the values of the elements as the number of rows and columns,
respectively. For example,
eye (3) => 1 0 0 0 1 0 0 0 1 The following expressions all produce the same result:
eye (2) == eye (2, 2) == eye (size ([1, 2; 3, 4]) The optional argument class, allows val = zeros (n,m, "uint8") For compatibility with MATLAB, calling |
ones (x) | Built-in Function |
ones (n, m) | Built-in Function |
ones (n, m, k, ...) | Built-in Function |
ones (..., class) | Built-in Function |
Return a matrix or N-dimensional array whose elements are all 1.
The arguments are handled the same as the arguments for eye .
If you need to create a matrix whose values are all the same, you should
use an expression like
val_matrix = val * ones (n, m) The optional argument class, allows val = ones (n,m, "uint8") |
zeros (x) | Built-in Function |
zeros (n, m) | Built-in Function |
zeros (n, m, k, ...) | Built-in Function |
zeros (..., class) | Built-in Function |
Return a matrix or N-dimensional array whose elements are all 0.
The arguments are handled the same as the arguments for eye .
The optional argument class, allows val = zeros (n,m, "uint8") |
repmat (A, m, n) | Function File |
repmat (A, [m n]) | Function File |
Form a block matrix of size m by n, with a copy of matrix A as each element. If n is not specified, form an m by m block matrix. |
rand (x) | Loadable Function |
rand (n, m) | Loadable Function |
rand ("seed" , x)
|
Loadable Function |
Return a matrix with random elements uniformly distributed on the
interval (0, 1). The arguments are handled the same as the arguments
for eye . In
addition, you can set the seed for the random number generator using the
form
rand ("seed", x) where x is a scalar value. If called as
rand ("seed")
|
randn (x) | Loadable Function |
randn (n, m) | Loadable Function |
randn ("seed" , x)
|
Loadable Function |
Return a matrix with normally distributed random elements. The
arguments are handled the same as the arguments for eye . In
addition, you can set the seed for the random number generator using the
form
randn ("seed", x) where x is a scalar value. If called as
randn ("seed")
|
The rand
and randn
functions use separate generators.
This ensures that
rand ("seed", 13); randn ("seed", 13); u = rand (100, 1); n = randn (100, 1);
and
rand ("seed", 13); randn ("seed", 13); u = zeros (100, 1); n = zeros (100, 1); for i = 1:100 u(i) = rand (); n(i) = randn (); end
produce equivalent results.
Normally, rand
and randn
obtain their initial
seeds from the system clock, so that the sequence of random numbers is
not the same each time you run Octave. If you really do need for to
reproduce a sequence of numbers exactly, you can set the seed to a
specific value.
If it is invoked without arguments, rand
and randn
return a
single element of a random sequence.
The rand
and randn
functions use Fortran code from
RANLIB, a library of fortran routines for random number generation,
compiled by Barry W. Brown and James Lovato of the Department of
Biomathematics at The University of Texas, M.D. Anderson Cancer Center,
Houston, TX 77030.
randperm (n) | Function File |
Return a row vector containing a random permutation of the integers from 1 to n. |
diag (v, k) | Built-in Function |
Return a diagonal matrix with vector v on diagonal k. The
second argument is optional. If it is positive, the vector is placed on
the k-th super-diagonal. If it is negative, it is placed on the
-k-th sub-diagonal. The default value of k is 0, and the
vector is placed on the main diagonal. For example,
diag ([1, 2, 3], 1) => 0 1 0 0 0 0 2 0 0 0 0 3 0 0 0 0 |
The functions linspace
and logspace
make it very easy to
create vectors with evenly or logarithmically spaced elements.
See Ranges.
linspace (base, limit, n) | Built-in Function |
Return a row vector with n linearly spaced elements between
base and limit. The number of elements, n, must be
greater than 1. The base and limit are always included in
the range. If base is greater than limit, the elements are
stored in decreasing order. If the number of points is not specified, a
value of 100 is used.
The |
logspace (base, limit, n) | Function File |
Similar to linspace except that the values are logarithmically
spaced from
10^base to 10^limit.
If limit is equal to pi, the points are between 10^base and pi, not 10^base and 10^pi, in order to be compatible with the corresponding MATLAB function. |
warn_neg_dim_as_zero | Built-in Variable |
If the value of warn_neg_dim_as_zero is nonzero, print a warning
for expressions like
eye (-1) The default value is 0. |
warn_imag_to_real | Built-in Variable |
If the value of warn_imag_to_real is nonzero, a warning is
printed for implicit conversions of complex numbers to real numbers.
The default value is 0.
|