The relevant IEEE standard defines a numeric constant NaN (not a number) and prescribes that NaN should compare as not equal to itself. Why is that? All the languages I'm familiar with implement this rule.

In computing, NaN (/ næn /), standing for Not a Number, is a particular value of a numeric data type (often a floating-point number) which is undefined as a number, such as the result of 0/0.

JavaScript automatic type conversion convert NaN into number, so checking if a number is not a number will always b false. and NaN !== NaN will be true. This behaviour is specified by the IEEE-754 standard (which the JavaScript spec follows in this respect).

6 days ago · To tell if a value is NaN, use Number.isNaN() or isNaN() to most clearly determine whether a value is NaN — or, since NaN is the only value that compares unequal to itself, you can perform a self-comparison like x !== x.

Jul 24, 2013 · In numpy there are nan, NaN and NAN. What's the sense of having all three, do they differ or any of these can be used interchangeably? It's just convenient. They're exactly the same. Different operating systems and programming languages may have different string representations of NaN: nan . NaN . NaN% . NAN . NaNQ . NaNS . qNaN . sNaN.

May 9, 2023 · In Python, the float type has nan. nan stands for "not a number" and is defined by the IEEE 754 floating-point standard. In the sample code of this article, math, pandas, and NumPy are imported as follows. Note that None, which represents the absence of a value, is different from nan. For more information on None, see the following article.

Dec 8, 2021 · In JavaScript, this question arises that what is the difference between NaN!=NaN and NaN!==NaN? The answer to this question is that for the purpose of NaN, both of them produce the same answer. Both will result in true. This is due to the variable values of NaN. NaN is not equal to NaN.

NaN表示不是一个数字（Not a Number），它是一种特殊的浮点数值。 NaN通常用于表示数学运算无法产生有意义的结果的情况，例如0除以0或对负数求平方根等。 NaN与任何其他值（包括NaN本身）进行比较的结果都是false，包括NaN == NaN。 这是因为NaN被定义为不等于任何其他值，甚至不等于它自己。 这是由于NaN的特殊性质导致的。 NaN的比较结果为false的原因是 …

Mar 31, 2022 · The macro NAN expands to constant expression of type float which evaluates to a quiet not-a-number (QNaN) value. If the implementation does not support QNaNs, this macro constant is not defined. There are many different NaN …

Dec 22, 2010 · NA means the error was already there when you imported the spreadsheet into R. NaN means you caused the error after importing the data. It's the third type of error that's really hard to catch. what are the first two?