LabVIEW Wiki - User contributions [en]

NaN

2007-11-26T03:25:01Z

David Boyd: typo, mine

'''NaN''' is the notation in LabVIEW for the floating-point value ''Not-a-Number''. LabVIEW implements the [http://grouper.ieee.org/groups/754/ IEEE-754 standard] for floating-point calculations, which specifies unique values for the outputs of mathematical operations which have no meaningful numerical result. A few examples of calculations which produce NaN are:

* division of zero by zero
* square root of a negative number
* division of an infinity by an infinity
* logarithm (any base) of a non-positive number
* any calculation which includes NaN as one of its operands

The last example above implies that any calculation sequence which generates NaN as an intermediate step will propagate NaN through all subsequent calculations. While this is generally true, there are exceptions (the LabVIEW '''Power of X''' primitive returns one for zero raised to NaN).

Another salient feature of the NaN value is that all comparison operations involving NaN return '''FALSE''', including the equality operator (in other words, NaN != NaN). LabVIEW provides the '''Not A Number/Path/Refnum?''' primitive, which is the proper way to test for NaN.
<center>
{| class="wikitable" align="center"
|-
! Not A Number/Path/Refnum? <br />primitive
|-
| [[Image:Nanfunc.png|center]]
|}
</center>

Floating-point controls, indicators, and block diagram constants support the direct entry of NaN (case-insensitive). Similarly, string-to-numeric and numeric-to-string primitives convert or format NaN without regard to format specifiers.

== External links ==

*[http://grouper.ieee.org/groups/754/ IEEE-754: Standard for Binary Floating-Point Arithmetic]
*[http://en.wikipedia.org/wiki/NaN Wikipedia entry on NaN]

NaN

2007-11-26T03:24:17Z

David Boyd: Reverted edits by David Boyd (Talk); changed back to last version by Michael_Aivaliotis

NaN

2007-11-26T03:23:28Z

David Boyd: typo (mine)

'''NaN''' is the notation in LabVIEW for the floating-point value ''Not-a-Number''. LabVIEW implements the [http://grouper.ieee.org/groups/754/ IEEE-754 standard] for floating-point calculations, which specifies unique values for the outputs of mathematical operations which have no meaningful numerical result. A few examples of calculations which produce NaN are:

* division of zero by zero
* square root of a negative number
* division of an infinity by an infinity
* logarithm (any base) of a non-positive number
* any calculation which includes NaN as one of its operands

The last example above implies that any calculation sequence which generates NaN as an intermediate step will propagate NaN through all subsequent calculations. While this is generally true, there are exceptions (the LabVIEW '''Power of X''' primitive returns one for zero raised to NaN).

Another salient feature of the NaN value is that all comparison operations involving NaN return '''FALSE''', including the equality operator (in other words, NaN != NaN). LabVIEW provides the '''Not A Number/Path/Refnum?''' primitive, which is the proper way to test for NaN.

Floating-point controls, indicators, and block diagram constants support the direct entry of NaN (case-insensitive). Similarly, string-to-numeric and numeric-to-string primitives convert or format NaN without regard to format specifiers.

== External links ==

*[http://grouper.ieee.org/groups/754/ IEEE-754: Standard for Binary Floating-Point Arithmetic]
*[http://en.wikipedia.org/wiki/NaN Wikipedia entry on NaN]

NaN

2007-11-17T05:59:25Z

David Boyd: First draft

'''NaN''' is the notation in LabVIEW for the floating-point value ''Not-a-Number''. LabVIEW implements the [http://grouper.ieee.org/groups/754/ IEEE-754 standard] for floating-point calculations, which specifies unique values for the outputs of mathematical operations which have no meaningful numerical result. A few examples of calculations which produce NaN are:

* division of zero by zero
* square root of a negative number
* division of an infinity by an infinity
* logarithm (any base) of a non-positive number
* any calculation which includes NaN as one of its operands

The last example above implies that any calculation sequence which generates NaN as an intermediate step will propagate NaN through all subsequent calculations. While this is generally true, there are exceptions (the LabVIEW '''Power of X''' primitive returns one for zero raised to NaN).

Another salient feature of the NaN value is that all comparison operations involving NaN return '''FALSE''', including the equality operator (in other words, NaN != NaN). LabVIEW provides the '''Not A Number/Path/Refnum?''' primitive, which is the proper way to test for NaN.

Floating-point controls, indicators, and block diagram constants support the direct entry of NaN (case-insensitive). Similarly, string-to-numeric and numeric-to-string primitives convert or format NaN without regard to format specifiers.

== External links ==

[http://grouper.ieee.org/groups/754/ IEEE-754: Standard for Binary Floating-Point Arithmetic]</br>
[http://en.wikipedia.org/wiki/NaN Wikipeda entry on NaN]