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Drop unused factor levels in a subsetted data frame
I have a data frame containing a factor . When I create a subset of this dataframe using subset or another indexing function, a new data frame is created. However, the factor variable retains all of its original levels, even when/if they do not exist in the new dataframe.
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Are braces necessary in one-line statements in JavaScript?
I once heard that leaving the curly braces in one-line statements could be harmful in JavaScript. I don't remember the reasoning anymore and a Google search did not help much.
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Why is there no logical xor in JavaScript?
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JavaScript traces its ancestry back to C, and C does not have a logical XOR operator. Mainly because it's not useful. Bitwise XOR is extremely useful, but in all my years of programming I have never needed a logical XOR.
If you have two boolean variables ...
numpy matrix vector multiplication [duplicate]
...ollowing normal matrix multiplication rules, a (n x 1) vector is expected, but I simply cannot find any information about how this is done in Python's Numpy module.
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Creating dataframe from a dictionary where entries have different lengths
....x:
import pandas as pd
import numpy as np
d = dict( A = np.array([1,2]), B = np.array([1,2,3,4]) )
pd.DataFrame(dict([ (k,pd.Series(v)) for k,v in d.items() ]))
Out[7]:
A B
0 1 1
1 2 2
2 NaN 3
3 NaN 4
In Python 2.x:
replace d.items() with d.iteritems().
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Difference between '..' (double-dot) and '…' (triple-dot) in range generation?
I've just started learning Ruby and Ruby on Rails and came across validation code that uses ranges:
5 Answers
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Retain precision with double in Java
The above code prints:
22 Answers
22
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Differences in boolean operators: & vs && and | vs ||
I know the rules for && and || but what are & and | ? Please explain these to me with an example.
11 Ans...
Behaviour of increment and decrement operators in Python
I notice that a pre-increment/decrement operator can be applied on a variable (like ++count ). It compiles, but it does not actually change the value of the variable!
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Virtual member call in a constructor
I'm getting a warning from ReSharper about a call to a virtual member from my objects constructor.
18 Answers
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