nan

After looking at another question on SO ( Using NaN in C++ ) I became curious about std::numeric_limits<double>::signaling_NaN() . I could not get signaling_NaN to throw an exception. I thought perhaps by signaling it really meant a signal so I tried catching SIGFPE but nope... Here is my code: double my_nan = numeric_limits<double>::signaling_NaN(); my_nan++; my_nan += 5; my_nan = my_nan / 10; my_nan = 15 / my_nan; cout << my_nan << endl; numeric_limits<double>::has_signaling_NaN evaluates to true, so it is implemented on my system. Any ideas? I am using ms visual studio .net 2003's C++

I know that NaN stands for Not a Number. But, I have trouble understanding when and why Oracle adds this to a row. Is it when it encounters a value less than 0 like a negative number or when its a garbage value. From the documentaton : The Oracle Database numeric data types store positive and negative fixed and floating-point numbers, zero, infinity, and values that are the undefined result of an operation—"not a number" or NAN . As far as I'm aware you can only get NaN in a binary_float or binary_double column; those data types have their own literals for NaN too , and there's an is nan

This is more of a 'Can you explain this' type of question than it is anything else. I came across a problem at work where we were using NaN values in a table, but when the table was sorted, it came out in a very strange, strange manner. I figured NaN was mucking up something so I wrote up a test application to see if this is true. This is what I did. static void Main(string[] args) { double[] someArray = { 4.0, 2.0, double.NaN, 1.0, 5.0, 3.0, double.NaN, 10.0, 9.0, 8.0 }; foreach (double db in someArray) { Console.WriteLine(db); } Array.Sort(someArray); Console.WriteLine("\n\n"); foreach

I'm trying to test if one of my variables is pd.NaT. I know it is NaT, and still it won't pass the test. As an example, the following code prints nothing : a=pd.NaT if a == pd.NaT: print("a not NaT") Does anyone have a clue ? Is there a way to effectively test if a is NaT? Pandas NaT behaves like a floating-point NaN , in that it's not equal to itself. Instead, you can use pandas.isnull : In [21]: pandas.isnull(pandas.NaT) Out[21]: True This also returns True for None and NaN. Technically, you could also check for Pandas NaT with x != x , following a common pattern used for floating-point NaN.

This question already has an answer here: What is the rationale for all comparisons returning false for IEEE754 NaN values? 13 answers Why are these two different? var x = NaN; //e.g. Number("e"); alert(isNaN(x)); //true (good) alert(x == NaN); //false (bad) Nothing is equal to NaN . Any comparison will always be false . In both the strict and abstract comparison algorithms, if the types are the same, and either operand is NaN , the result will be false . If Type(x) is Number, then If x is NaN , return false . If y is NaN , return false . In the abstract algorithm, if the types are different,

I am using the spark 2.0.1 and want to fill nan values with the last good known value in the column. The only reference for spark I could find Spark / Scala: forward fill with last observation or Fill in null with previously known good value with pyspark which seem to use RDD. I would rather like to stay in the data frame / dataset world and possible handle multiple nan values. Is this possible? My assumption is that the data (initially loaded from e.g. a CSV file is ordered by time and this order is preserved in the distributed setting e.g. filling by close / last good known value is correct.

I am trying to set members of an array that are below a threshold to nan. This is part of a QA/QC process and the incoming data may already have slots that are nan. So as an example my threshold might be -1000 and hence I would want to set -3000 to nan in the following array x = np.array([np.nan,1.,2.,-3000.,np.nan,5.]) This following: x[x < -1000.] = np.nan produces the correct behavior, but also a RuntimeWarning, but the overhead of disabling the warning warnings.filterwarnings("ignore") ... warnints.resetwarnings() is kind of heavy an potentially a bit unsafe. Trying to index twice with