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Using numpy to build an array of all combinations of two arrays
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131
In newer version of numpy (>1.8.x), numpy.meshgrid() provides a much faster implementation:
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Append a NumPy array to a NumPy array
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234
In [1]: import numpy as np
In [2]: a = np.array([[1, 2, 3], [4, 5, 6]])
In [3]: b = np.array(...
finding and replacing elements in a list
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>>> a= [1, 2, 3, 4, 5, 1, 2, 3, 4, 5, 1]
>>> for n, i in enumerate(a):
... if i == 1:
... a[n] = 10
...
>>> a
[10, 2, 3, 4, 5, 10, 2, 3, 4, 5, 10]
...
Sample random rows in dataframe
...rnorm(20), nrow=10))
> df
X1 X2
1 0.7091409 -1.4061361
2 -1.1334614 -0.1973846
3 2.3343391 -0.4385071
4 -0.9040278 -0.6593677
5 0.4180331 -1.2592415
6 0.7572246 -0.5463655
7 -0.8996483 0.4231117
8 -1.0356774 -0.1640883
9 -0.3983045 0.7157506
10 -0.9060305 2.3234...
How to update gradle in android studio?
...Official links
Version Compatibility
Migrate to Android Plugin for Gradle 3.0.0
Find out the latest version of Gradle
Info about the Gradle Wrapper
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Pandas index column title or name
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394
You can just get/set the index via its name property
In [7]: df.index.name
Out[7]: 'Index Tit...
how to change default python version?
I have installed python 3.2 in my mac. After I run /Applications/Python 3.2/Update Shell Profile.command , it's confusing that when I type python -V in Terminal it says that Python 2.6.1 , how can I change the default python version?
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Apply a function to every row of a matrix or a data frame
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You simply use the apply() function:
R> M <- matrix(1:6, nrow=3, byrow=TRUE)
R> M
[,1] [,2]
[1,] 1 2
[2,] 3 4
[3,] 5 6
R> apply(M, 1, function(x) 2*x[1]+x[2])
[1] 4 10 16
R>
This takes a matrix and applies a (silly) function to each row. You pass extr...
Why are these numbers not equal?
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359
General (language agnostic) reason
Since not all numbers can be represented exactly in IEEE f...
What is Weak Head Normal Form?
...re not in normal form:
1 + 2 -- we could evaluate this to 3
(\x -> x + 1) 2 -- we could apply the function
"he" ++ "llo" -- we could apply the (++)
(1 + 1, 2 + 2) -- we could evaluate 1 + 1 and 2 + 2
Weak head normal form
An expression in weak head normal ...