大约有 43,400 项符合查询结果（耗时：0.0404秒） [XML]
Understanding exactly when a data.table is a reference to (vs a copy of) another data.table
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2 Answers
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Iterating over every two elements in a list
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Creating dataframe from a dictionary where entries have different lengths
...hon 3.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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How do I change the default port (9000) that Play uses when I execute the “run” command?
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All combinations of a list of lists
...eed itertools.product:
>>> import itertools
>>> a = [[1,2,3],[4,5,6],[7,8,9,10]]
>>> list(itertools.product(*a))
[(1, 4, 7), (1, 4, 8), (1, 4, 9), (1, 4, 10), (1, 5, 7), (1, 5, 8), (1, 5, 9), (1, 5, 10), (1, 6, 7), (1, 6, 8), (1, 6, 9), (1, 6, 10), (2, 4, 7), (2, 4, 8), (...
Difference between numpy.array shape (R, 1) and (R,)
... how to interpret the data buffer.
For example, if we create an array of 12 integers:
>>> a = numpy.arange(12)
>>> a
array([ 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11])
Then a consists of a data buffer, arranged something like this:
┌────┬────┬──...
Does assignment with a comma work?
Why does aaa = 1,2,3 work and set the value of aaa to 1 ?
4 Answers
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Apply a function to every row of a matrix or a data frame
Suppose I have a n by 2 matrix and a function that takes a 2-vector as one of its arguments. I would like to apply the function to each row of the matrix and get a n-vector. How to do this in R?
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Counting the occurrences / frequency of array elements
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LISTAGG in Oracle to return distinct values
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