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nan [Mon Jan 11 23:16:53 2010] Alexander |
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- | ====== NaN ====== | + | ====== Missing Values (NaN) in Tables and Calculations ====== |

- | 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. | + | In computing, NaN, which stands for Not a Number, is a value or symbol that is usually produced as a 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. | + | 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. |

- | 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'' | + | ==== How does a NaN appear? ==== |

- | ==== How is a NaN created? ==== | + | There are three kinds of operations which return NaN: |

- | | + | - Operations with a NaN as at least one operand, e.g. '' |

- | There are three kinds of operation which return NaN: | + | |

- | - Operations with a NaN as at least one operand | + | |

- Indeterminate forms | - Indeterminate forms | ||

- | * The divisions 0/0, ∞/∞, ∞/-∞, -∞/∞, -∞/-∞ | + | * Divisions ''0/0, ∞/∞, ∞/-∞, -∞/∞, -∞/-∞'' |

- | * The multiplications 0×∞ and 0×-∞ | + | * Multiplications ''∞, 0*(-∞)'' |

- | * The power 1^∞ | + | * Power ''1^∞'' |

- | * The additions ∞ + (-∞), (-∞) + ∞ and equivalent subtractions. | + | * Additions ''∞+(-∞), (-∞)+∞'' and equivalent subtractions. |

- | - Real operations with complex results: | + | - Real operations with complex results |

- | * The square root of a negative number | + | * Square root of a negative number |

- | * The logarithm of a negative number | + | * Logarithm of a negative number |

- | * The tangent of an odd multiple of 90 degrees (or //π///2 radians) | + | * 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. | + | * Inverse sine or cosine of a number which is less than -1 or greater than +1. |

- | | + | |

- | ===== NaN in Tables ===== | + | |

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

- | | + | |

- | Statistical functions ignores NaN values in tables. | + | |

- | | + | |

- | ===== NaN in Expressions ===== | + | |

- | You can use a predefined constants '' | + | |

- | | + | |

- | ===== Examples ===== | + | |

+ | === Examples === | ||

^ Expression | ^ Expression | ||

| '' | | '' | ||

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| '' | | '' | ||

| '' | | '' | ||

+ | |||

+ | ===== NaN in MagicPlot Tables ===== | ||

+ | In MagicPlot NaN is also used to represent empty cells in [[table|Tables]]. | ||

+ | |||

+ | Statistical functions ignore NaN values in Tables. | ||

+ | |||

+ | ===== NaN in Expressions ===== | ||

+ | You can use predefined constants '' | ||

+ | |||

+ | The '' | ||

+ | |||

+ | === Example === | ||

+ | * If you set a [[set_column_formula|Column Formula]] '' |

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

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