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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, especially in floating-point calculations. 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. |

- | NaNs may also be used to represent missing values in table. | + | 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. |

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

+ | There are three kinds of operations which return NaN: | ||

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

+ | - Indeterminate forms | ||

+ | * Divisions '' | ||

+ | * Multiplications '' | ||

+ | * Power '' | ||

+ | * Additions '' | ||

+ | - Real operations with complex results | ||

+ | * Square root of a negative number | ||

+ | * Logarithm of a negative number | ||

+ | * Tangent of an odd multiple of 90 degrees (or //π///2 radians) | ||

+ | * Inverse sine or cosine of a number which is less than -1 or greater than +1. | ||

+ | |||

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

^ Expression | ^ Expression | ||

| '' | | '' | ||

| '' | | '' | ||

| '' | | '' | ||

+ | | '' | ||

+ | | '' | ||

+ | |||

+ | ===== 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.1263203367.txt.gz · Last modified: Sun Nov 8 12:20:32 2015 (external edit)

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