GNU Octave: Numeric Data Types

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## 4 Numeric Data Types

A numeric constant may be a scalar, a vector, or a matrix, and it may contain complex values.

The simplest form of a numeric constant, a scalar, is a single number that can be an integer, a decimal fraction, a number in scientific (exponential) notation, or a complex number. Note that by default numeric constants are represented within Octave in double-precision floating point format (complex constants are stored as pairs of double-precision floating point values). It is, however, possible to represent real integers as described in Integer Data Types. Here are some examples of real-valued numeric constants, which all have the same value:

    105
    1.05e+2
    1050e-1

To specify complex constants, you can write an expression of the form

    3 + 4i
    3.0 + 4.0i
    0.3e1 + 40e-1i

all of which are equivalent. The letter ‘`i`’ in the previous example stands for the pure imaginary constant, defined as `sqrt (-1)`.

For Octave to recognize a value as the imaginary part of a complex constant, a space must not appear between the number and the ‘`i`’. If it does, Octave will print an error message, like this:

    octave:13> 3 + 4 i

    parse error:

      syntax error

    >>> 3 + 4 i
              ^

You may also use ‘`j`’, ‘`I`’, or ‘`J`’ in place of the ‘`i`’ above. All four forms are equivalent.

: double (x)

  Convert x to double precision type.

  See also: single.

: complex (x)
: complex (re, im)

  Return a complex value from real arguments.

  With 1 real argument x, return the complex result `x + 0i`.

  With 2 real arguments, return the complex result `re + im`. `complex` can often be more convenient than expressions such as `a + i*b`. For example:

      complex ([1, 2], [3, 4])
        ⇒ [ 1 + 3i   2 + 4i ]

  See also: real, imag, iscomplex, abs, arg.

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