nan

问题 My program during calculation can generate nan or -nan values. I check if the values are nan / -nan using isnan method. I also have to distinguish if the nan value is positive or negative ( nan or -nan ). How can I do this? Added:I need crossplatform solution for WIN and for Unix/Linux 回答1: Try signbit from <math.h> : Description signbit() is a generic macro which can work on all real floating-point types. It returns a nonzero value if the value of x has its sign bit set. ... NaNs and

问题 I'm using this post to extend nan values with some extra info and this post to modify std::cout behaviour and display this extra info. Here is the code defining the functions and NumPut class: #include <iostream> #include <assert.h> #include <limits> #include <bitset> #include <cmath> #include <locale> #include <ostream> #include <sstream> template <typename T> void showValue( T val, const std::string& what ) { union uT { T d; unsigned long long u; }; uT ud; ud.d = val; std::bitset<sizeof(T)

问题 I have a long complicated source code and I need to find the exact location at which a variable value set to nan. So I need the compiler to throw an exception at that point. This question has been asked before. I found the following answer as a good answer. This code works well in .net 3.5.But when I use .net 4, this solution doesn't work correctly. Even when I Enable "break when an exception is thrown" in the debugger, the exception can't be located in the code. Any idea? using System; using

问题 I want to convert signalling NaN to quiet NaN in C. Could anybody suggest a method? Thanks. 回答1: I guess I'll expand on my comment and provide a solution. The tricky part here is being able to read/compare the sNaN without triggering an exception. After all it's called "signalling" for a reason. Wikipedia says that even comparison operations on sNaN will trigger an exception. So a direct use of number != number or isnan(value) probably don't work because they invoke comparisons and will

问题 This is an interesting topic given it could lead to unexpected results in code. Suppose I had an array as follows; import numpy as np X = np.array([np.nan,np.nan,np.nan,np.nan,np.nan]) np.nanmean(X) rightly returns a warning that the averaging slice is empty and returns nan. However, when doing a summation of the array, np.nansum(X) , it returns 0.0 . Now while mathematically true (the sum of nothing is 0), the result expected to be returned might be np.nan. For an example, I have a function

问题 R beginner here. I would like to convert 0s into NaNs in these 6 of the 9 columns: "int_t", "ext_t", "int_h", ext_h", "db", and "pa". Thanks. 回答1: There is an is.na.data.frame function, but no is.na<-.data.frame , so ... only perhaps: is.na( dfrm[ , c( "int_t", "ext_t", "int_h", ext_h", "db", "pa")] ) <- dfrm[ , c( "int_t", "ext_t", "int_h", ext_h", "db", "pa")]==0 You should provide a test case. (But now that I have tested it I think ti should succeed.) 回答2: Try nm <- c("int_t", "ext_t",

问题 I'm not sure what I'm doing wrong in my code but I can't get it to run properly...the tester keeps returning NaN instead of what's supposed to be expected. The goal of this exercise is to print all real solutions to the quadratic equation. solution1 should return the smaller solution and solution2 should return the smaller solution. Here's my class. public class QuadraticEquation { private int a; private int b; private int c; private boolean hasSolutions; private double discriminant = (b * b)

问题 I have a table in matlab R2015b with the following data var 1 var 2 var 3 Row1 1 NaN 2 Row2 2 4 NaN I'd like to replace all NaN's in my table with 0's - so something along these lines: Assume my table is called A newTableA = rowfun(@(x) x(isnan(x)) = 0,A,'ExtractCellData',true); I suppose I could convert my table to a new matrix B, perform, B(isnan(B)) = 0, and convert back to a table, but I thought there might be a more efficient way. 回答1: Just loop over the variables: t = array2table([1 nan

问题 I am developing a html page that takes date and displays day. I am using a formula called Zeller's congruence. But in JavaScript the formula returns the Result "NaN". I googled the problem. Couldn't figure out the solution. Here is the html that takes values. <form method="post"> <br/> day:<input id="dd" name="dd" type="text"/><br/> month:<input id="mm" name="mm" type="text"/><br/> year:<input id="yy" name="yy" type="text"/><br/> <input type="submit" value="go" onclick="day()"/><br/> </form>

问题 A program repeats some calculation over an array of double s. Then something unfortunate happens and NaN get produced... It starts running much slower after this. -ffast-math does not change a thing. Why does it happen with -ffast-math ? Shouldn't it prevent throwing floating-point exceptions and just proceed and churn out NaN s at the same rate as usual numbers? Simple example: nan.c #include <stdio.h> #include <math.h> int main() { long long int i; double a=-1,b=0,c=1; for(i=0; i<100000000;