nan

问题 I'm writing Python 2.6 code that interfaces with NI TestStand 4.2 via COM in Windows. I want to make a "NAN" value for a variable, but if I pass it float('nan') , TestStand displays it as IND . Apparently TestStand distinguishes between floating point "IND" and "NAN" values. According to TestStand help: IND corresponds to Signaling NaN in Visual C++, while NAN corresponds to QuietNaN That implies that Python's float('nan') is effectively a Signaling NaN when passed through COM. However, from

问题 I have a data series which looks like this: print mys id_L1 2 NaN 3 NaN 4 NaN 5 NaN 6 NaN 7 NaN 8 NaN I would like to check is all the values are NaN. My attempt: pd.isnull(mys).all() Output: True Is this the correct way to do it? 回答1: Yes, that's correct, but I think a more idiomatic way would be: mys.isnull().all() 回答2: This will check for all columns.. mys.isnull().values.all(axis=0) 来源： https://stackoverflow.com/questions/33147158/pandas-check-if-all-values-are-nan-in-series

问题 I'm trying to add the values of two arrays in javascript eg. [1,2,1] + [3,2,3,4] The answer should be 4,4,4,4 but I'm either getting 4,4,4 or 4,4,4,NaN if I change the 1st array length to 4. I know a 4th number needs to be in the 1st array, but i can't figure out how to tell javascript to make it 0 rather then undefined if there is no number. 回答1: Use isNaN to ensure the value does not evaluate to NaN in arithmetic operations. This will safely add two numbers such that if one of them is not a

问题 While nan == nan is always False , in many cases people want to treat them as equal, and this is enshrined in pandas.DataFrame.equals: NaNs in the same location are considered equal. Of course, I can write def equalp(x, y): return (x == y) or (math.isnan(x) and math.isnan(y)) However, this will fail on containers like [float("nan")] and isnan barfs on non-numbers (so the complexity increases). So, what do people do to compare complex Python objects which may contain nan ? PS . Motivation:

问题 I read this and this. The quintessence is that one can throw a SIGFPE if a nan is produced by including fenv.h and enabling all floating point exceptions but FE_INEXACT by feenableexcept(FE_ALL_EXCEPT & ~FE_INEXACT); Thus, the code changes form int main () { double dirty = 0.0; double nanvalue = 0.0/dirty; return 0; } to #include <fenv.h> int main () { feenableexcept(FE_ALL_EXCEPT & ~FE_INEXACT); // Enable all floating point exceptions but FE_INEXACT double dirty = 0.0; double nanvalue = 0.0

问题 I have an application in which a code area produces NAN values. I have to compare the values for equality and based on that execute the rest of the code.How to compare two NAN values in C++ for equality? 回答1: Assuming an IEEE 754 floating point representation, you cannot compare two NaN values for equality. NaN is not equal to any value, including itself. You can however test if they are both NaN with std::isnan from the <cmath> header: if (std::isnan(x) && std::isnan(y)) { // ... } This is

问题 I can get remove all nan in x numpy array and from related y array with a mask or y = y[~np.isnan(x)] x = x[~np.isnan(x)] Now, I need only remove parts when there are many (let's say 20 NaNs in a row). Does anyone know how to handle this issue? 回答1: There's a bit of ambiguity in the question, but regardless, it'll be nice to answer both versions. I'm not sure if you meant that you need to remove sections where there are more than 20 consecutive NaNs on 1D data, or if you meant that you need

问题 Is it possible to use numpy.nanargmin , so that it returns numpy.nan , on columns where there are only nans in them. Right now, it raises a ValueError , when that happens. And i cant use numpy.argmin , since that will fail when there are only a few nans in the column. http://docs.scipy.org/doc/numpy/reference/generated/numpy.nanargmin.html says that the ValueError is raised for all-nan slices. In that case, i want it to return numpy.nan (just to further mask the "non-data" with nans) this

问题 I have this code: http://pastebin.com/Sd9WKZFr When i call something like rate(60, -6000, 120000) it returns me a NAN result, but the same function on MS Excel returns me 0,04678... . I have the same problem trying -5000, -4000, -3000 and -2000. When i debug the code, i see that about the 8/9 iteration, the line number 29 begins to return a NAN result, making all of other results to turn NAN too. BUT, when i call something like rate(60, -1000, 120000) it returns me a float -0.02044... ,

问题 I have a set of balloons that I am trying to get to bounce off of each other like balls. When I start to move them and then detect collision, the routine for the collisions eventually returns a NAN for the velocity of the balloons. I end up with a position of something like x=270, y= -nan(0x400000). I've been looking at the code all day and I still can't find the error, any help would be appreciated. Here's the code: - (void)MoveBalloons { for (CurBalloon=1; CurBalloon <= NumBalloons; +