nan

问题 This question already has answers here : undefined reference to sqrt (or other mathematical functions) (5 answers) Closed 4 months ago . Part of my program is to calculate sqrt of float number. When I write sqrt(1.0f); I success to compile the program,but when I write sqrt(-1.0f); the compilation fails with undefined reference to 'sqrt' - I suppose that in this case the nan value will be returned... I compile the program uing gcc. When I compile it with visual studio it is compiled

问题 I have found here an excellent solution for creating relationships when migrating a model. I came across an odd problem within the model itself. -(BOOL)createRelationshipsForDestinationInstance:(NSManagedObject *)dInstance entityMapping:(NSEntityMapping *)mapping manager:(NSMigrationManager *)manager error:(NSError *__autoreleasing *)error { NSError *superError = nil; BOOL ismappingSuccess = [super createRelationshipsForDestinationInstance:dInstance entityMapping:mapping manager:manager error

问题 I have a .txt file with the following data: sampleF.txt --> (tab delimited) MSFT 200 100 APPL 10 NULL AMZN 20 40 I need to read this data using textscan . I am facing a problem while reading the NULL data. Using treatasempty param, I can read it as 0. But I want to read it as NaN . Please help! Thanks! fName = '.....\sampleF.txt' [fid, message] = fopen(fName) ; if fid < 0, disp(message), else datatxt = textscan(fid, '%q %d %d', 'Delimiter', '\t','treatAsEmpty','NULL'); datatxt = [ datatxt {1}

问题 I have two lists of numbers which I'm using matplotlib to graph in Python. However if one of the lists begins with the value of nan, matplotlib will not graph any of the 15k+ points I have. However if there is a nan value somewhere in the list after the first value, it simply skips it and graphs the other points fine. I'm curious how to work around this without changing the first nan value. 回答1: you can use the numpy.isnan function to mask your list: a=np.array([np.nan,1,2,3,4,np.nan]) mask=

问题 Trying to deal with missing data, I wrote the following model and ran it. The output is given below. Why does the training step on NaN expected values, which are masked by loss_0_where_nan (and the history shows that the loss is indeed evaluated to 0.0 ), nonetheless introduce NaN weights in the weight matrices of both hidden and max_min_pred ? I first thought this might be some weighting of individual parameter learning with output values, which I thought might be specific to the Adadelta

问题 More of a general MATLAB question than looking for programming advice -- if I have: y = cellfun(@(x)sum(x(:)), Z, 'un', 0); where there are a combinations of NaN 's and real numbers in each cell matrix, when I sum all elements of those matrices per cell, will I always get total = NaN because there are NaN 's in there, or will they be ignored and just sum the real numbers. The reason I ask is because I am getting: y = [NaN] [NaN] [NaN] [NaN] [NaN] [NaN] [NaN] [NaN] [NaN] an example cell matrix

问题 Let's say I have this table Type | Killed | Survived Dog 5 2 Dog 3 4 Cat 1 7 Dog nan 3 cow nan 2 One of the value on Killed is missing for [Type] = Dog . I want to impute the mean in [Killed] for [Type] = Dog . My code is as follow: Search for the mean df[df['Type'] == 'Dog'].mean().round() This will give me the mean (around 2.25) Impute the mean (This is where the problem begins) df.loc[(df['Type'] == 'Dog') & (df['Killed'])].fillna(2.25, inplace = True) The code runs, but the value is not

问题 After reading an Excel spreadsheet in Matlab I unfortunately have NaNs included in my resulting table. So for example this Excel table: would result in this table: where an additional column of NaNs occurs. I tried to remove the NaNs with the following code snippet: measurementCells = readtable('MWE.xlsx','ReadVariableNames',false,'ReadRowNames',true); measurementCells = measurementCells(any(isstruct(measurementCells('TIME',1)),1),:); However this results in a 0x6 table, without any values

问题 In Javascript: NaN === NaN; // false I was trying to determine when isNaN(foo) is not just equivalent to +foo "is" NaN . But I don't know how to tell if something is NaN except by using isNaN , which says yes for many things, none of which === NaN. So I think the right way to do this would be to work around other possibilities: typeof NaN === 'number' // true Therefore I think typeof(foo) === 'number' && isNaN(foo) Is the closest to what I am thinking of. It makes sense since it makes sense

问题 Hints and allegations abound that arithmetic with NaNs can be 'slow' in hardware FPUs. Specifically in the modern x64 FPU, e.g on a Nehalem i7, is that still true? Do FPU multiplies get churned out at the same speed regardless of the values of the operands? I have some interpolation code that can wander off the edge of our defined data, and I'm trying to determine whether it's faster to check for NaNs (or some other sentinel value) here there and everywhere, or just at convenient points. Yes,