nan

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In computing, NaN, which stands for Not a Number, is a value or symbol that is usually produced as the result of an operation on invalid input operands. For example, most floating-point units are unable to explicitly calculate the square root of negative numbers, and will instead indicate that the operation was invalid and return a NaN result.

An invalid operation is not the same as an arithmetic overflow (which returns a positive or negative infinity). Arithmetic operations involving NaN always produce NaN, allowing the value to propagate through a calculation so that errors can be detected at the end without extensive testing during intermediate stages.

A NaN does not compare equal to any number or NaN. You can therefore test whether a variable has a NaN value by comparing it to itself, thus if `x == x`

gives false (0) then x is a NaN code.

There are three kinds of operation which return NaN:

- Operations with a NaN as at least one operand
- Indeterminate forms
- The divisions 0/0, ∞/∞, ∞/-∞, -∞/∞, -∞/-∞
- The multiplications 0×∞ and 0×-∞
- The power 1^∞
- The additions ∞ + (-∞), (-∞) + ∞ and equivalent subtractions.

- Real operations with complex results:
- The square root of a negative number
- The logarithm of a negative number
- The tangent of an odd multiple of 90 degrees (or
*π*/2 radians) - The inverse sine or cosine of a number which is less than -1 or greater than +1.

In MagicPlot NaN also is used to represent empty cells in tables.

Statistical functions ignores NaN values in tables.

You can use a predefined constants `NaN`

, `nan`

or `NAN`

in expressions to indicate NaN value.

Expression | Result |
---|---|

`0^0` | `1` |

`0/0` | `NaN` |

`sqrt(-1)` | `NaN` |

`1/0` | `Infinity` |

`-1/0` | `-Infinity` |

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nan.1263241013.txt.gz · Last modified: Sun Nov 8 12:20:32 2015 (external edit)

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