nan

问题 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

问题 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

问题 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. 回答1: 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

问题 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. 回答1: 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

问题 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

问题 take a look at the code blew: #include <complex> #include <iostream> int main() { std::cout << std::pow( std::complex<double>(0,0), std::complex<double>(0,0) ) << "\n"; std::cout << std::pow( std::complex<double>(0,0), double(0) ) << "\n"; return 0; } g++(4.8.1) gives an output of (nan,nan) (-nan,-nan) while clang++(3.3) gives an out put of (-nan,-nan) (-nan,-nan) But I am expecting (1.0, 0.0). Can anyone give an explanation? 回答1: According to std::pow documentation Return value base raised

问题 Python 2.7.3 (default, Aug 1 2012, 05:14:39) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> x = float('nan') >>> id(x) == id(x) True >>> x == x False I'm interested in how nan != nan in python. And just to clarify, I know nan is supposed to behave like that by definition, I'm asking about how not about why. Where is that implemented? Is there any other object which behaves like that? 回答1: For the "where" part of your questions, look starting

问题 Python 2.7.3 (default, Aug 1 2012, 05:14:39) [GCC 4.6.3] on linux2 Type "help", "copyright", "credits" or "license" for more information. >>> x = float('nan') >>> id(x) == id(x) True >>> x == x False I'm interested in how nan != nan in python. And just to clarify, I know nan is supposed to behave like that by definition, I'm asking about how not about why. Where is that implemented? Is there any other object which behaves like that? 回答1: For the "where" part of your questions, look starting

问题 I have two CSV_files with hundreds of columns and I want to calculate Pearson correlation coefficient and p value for every same columns of two CSV_files. The problem is that when there is a missing data "NaN" in one column, it gives me an error. When ".dropna" removes nan value from columns, sometimes the shapes of X and Y are not equal (based on removed nan values) and I receive this error: "ValueError: operands could not be broadcast together with shapes (1020,) (1016,)" Question: If row

问题 I have two CSV_files with hundreds of columns and I want to calculate Pearson correlation coefficient and p value for every same columns of two CSV_files. The problem is that when there is a missing data "NaN" in one column, it gives me an error. When ".dropna" removes nan value from columns, sometimes the shapes of X and Y are not equal (based on removed nan values) and I receive this error: "ValueError: operands could not be broadcast together with shapes (1020,) (1016,)" Question: If row