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Questions tagged [nan]

NaN is an abbreviation for "Not a Number". NaN is sometimes not equal to itself.

NaN (Not a Number) is a value of the numeric data type representing an undefined or unrepresentable value, especially in floating-point calculations. Systematic use of NaNs was introduced by the IEEE 754 floating-point standard in 1985, along with the representation of other non-finite quantities such as infinity.

A common feature of NaN in many programming languages is that NaN is not equal to itself.

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pandas GroupBy columns with NaN (missing) values

I have a DataFrame with many missing values in columns which I wish to groupby: import pandas as pd import numpy as np df = pd.DataFrame({'a': ['1', '2', '3'], 'b': ['4', np.NaN, '6']}) In [4]: df.groupby('b').groups Out[4]: {'4': [0], '6':…
Gyula Sámuel Karli
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How to find which columns contain any NaN value in Pandas dataframe

Given a pandas dataframe containing possible NaN values scattered here and there: Question: How do I determine which columns contain NaN values? In particular, can I get a list of the column names containing NaNs?
Jesper - jtk.eth
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How to replace NaNs by preceding or next values in pandas DataFrame?

Suppose I have a DataFrame with some NaNs: >>> import pandas as pd >>> df = pd.DataFrame([[1, 2, 3], [4, None, None], [None, None, 9]]) >>> df 0 1 2 0 1 2 3 1 4 NaN NaN 2 NaN NaN 9 What I need to do is replace every NaN with the…
zegkljan
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Is it possible to set a number to NaN or infinity?

Is it possible to set an element of an array to NaN in Python? Additionally, is it possible to set a variable to +/- infinity? If so, is there any function to check whether a number is infinity or not?
Bob
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Why does typeof NaN return 'number'?

Just out of curiosity. It doesn't seem very logical that typeof NaN is number. Just like NaN === NaN or NaN == NaN returning false, by the way. Is this one of the peculiarities of JavaScript, or would there be a reason for this? Edit: thanks for…
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Why does isNaN(" ") (string with spaces) equal false?

In JavaScript, why does isNaN(" ") evaluate to false, but isNaN(" x") evaluate to true? I’m performing numerical operations on a text input field, and I’m checking if the field is null, "", or NaN. When someone types a handful of spaces into the…
IVR Avenger
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Python Pandas replace NaN in one column with value from corresponding row of second column

I am working with this Pandas DataFrame in Python. File heat Farheit Temp_Rating 1 YesQ 75 N/A 1 NoR 115 N/A 1 YesA 63 N/A 1 NoT 83 41 1 NoY …
edesz
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Replace None with NaN in pandas dataframe

I have table x: website 0 http://www.google.com/ 1 http://www.yahoo.com 2 None I want to replace python None with pandas NaN. I tried: x.replace(to_replace=None, value=np.nan) But I got: TypeError: 'regex' must be a string or a…
AdamNYC
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How to set a cell to NaN in a pandas dataframe

I'd like to replace bad values in a column of a dataframe by NaN's. mydata = {'x' : [10, 50, 18, 32, 47, 20], 'y' : ['12', '11', 'N/A', '13', '15', 'N/A']} df = pd.DataFrame(mydata) df[df.y == 'N/A']['y'] = np.nan Though, the last line fails and…
Mark Morrisson
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Why is NaN not equal to NaN?

The relevant IEEE standard defines a numeric constant NaN (not a number) and prescribes that NaN should compare as not equal to itself. Why is that? All the languages I'm familiar with implement this rule. But it often causes significant problems,…
max
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Why does Double.NaN==Double.NaN return false?

I was just studying OCPJP questions and I found this strange code: public static void main(String a[]) { System.out.println(Double.NaN==Double.NaN); System.out.println(Double.NaN!=Double.NaN); } When I ran the code, I got: false true How…
Maverick
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Fast check for NaN in NumPy

I'm looking for the fastest way to check for the occurrence of NaN (np.nan) in a NumPy array X. np.isnan(X) is out of the question, since it builds a boolean array of shape X.shape, which is potentially gigantic. I tried np.nan in X, but that seems…
Fred Foo
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C/C++ NaN constant (literal)?

Is this possible to assign a NaN to a double or float in C/C++? Like in JavaScript you do: a = NaN. So later you can check if the variable is a number or no.
exebook
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What is the difference between quiet NaN and signaling NaN?

I have read about floating-point and I understand that NaN could result from operations. But I can't understand what these are concepts exactly. What is the difference between them? Which one can be produced during C++ programming? As a programmer,…
JalalJaberi
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What is the difference between (NaN != NaN) and (NaN !== NaN)?

First of all I want to mention that I know how isNaN() and Number.isNaN() work. I am reading The Definite Guide by David Flanagan and he gives an example for how to check if the value is NaN: x !== x This will result in true if and only if x is…
Giorgi Nakeuri
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