Since the type of a variable may change during the execution of a
program, it can be necessary to do type checking at run-time. Doing this
also allows you to change the behavior of a function depending on the
type of the input. As an example, this naive implementation of abs
returns the absolute value of the input if it is a real number, and the
length of the input if it is a complex number.
function a = abs (x)
if (isreal (x))
a = sign (x) .* x;
elseif (iscomplex (x))
a = sqrt (real(x).^2 + imag(x).^2);
endif
endfunction
The following functions are available for determining the type of a variable.
Return true if x is a numeric object, i.e., an integer, real, or complex array. Logical and character arrays are not considered to be numeric.
See also: isinteger, isfloat, isreal, iscomplex, islogical, ischar, iscell, isstruct.
Return true if x is a non-complex matrix or scalar. For compatibility with matlab, this includes logical and character matrices.
Return true if x is a floating-point numeric object. Objects of class double or single are floating-point objects.
Return true if a is a numeric, logical, or character matrix. Scalars (1x1 matrices) and vectors (1xN or Nx1 matrices) are subsets of the more general N-dimensional matrix and
ismatrixwill return true for these objects as well.
Return true if x is a vector. A vector is a 2-D array where one of the dimensions is equal to 1. As a consequence a 1x1 array, or scalar, is also a vector.
Return true if x is a symmetric matrix within the tolerance specified by tol. The default tolerance is zero (uses faster code). Matrix x is considered symmetric if
norm (x-x.', Inf) / norm (x, Inf) <tol.See also: ishermitian, isdefinite.
Return true if x is Hermitian within the tolerance specified by tol. The default tolerance is zero (uses faster code). Matrix x is considered symmetric if
norm (x-x', Inf) / norm (x, Inf) <tol.See also: issymmetric, isdefinite.
Return 1 if x is symmetric positive definite within the tolerance specified by tol or 0 if x is symmetric positive semidefinite. Otherwise, return -1. If tol is omitted, use a tolerance of
100 * eps * norm (x, "fro")See also: issymmetric, ishermitian.
Return true if x is a logical object.