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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.

Built-in Function: double (x)

Convert x to double precision type.

Built-in Function: complex (x)
Built-in Function: 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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