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How to get a number of random elements from an array?
I am working on 'how to access elements randomly from an array in javascript'. I found many links regarding this. Like:
Get random item from JavaScript array
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How do I use itertools.groupby()?
...he part I didn't get is that in the example construction
groups = []
uniquekeys = []
for k, g in groupby(data, keyfunc):
groups.append(list(g)) # Store group iterator as a list
uniquekeys.append(k)
k is the current grouping key, and g is an iterator that you can use to iterate over the gro...
Circle line-segment collision detection algorithm?
...
Taking
E is the starting point of the ray,
L is the end point of the ray,
C is the center of sphere you're testing against
r is the radius of that sphere
Compute:
d = L - E ( Direction vector of ray, from start to en...
Simple (non-secure) hash function for JavaScript? [duplicate]
...) hash function written in (browser-compatible) JavaScript? Ideally I'd like something that, when passed a string as input, produces something similar to the 32 character hexadecimal string that's the typical output of MD5, SHA1, etc. It doesn't have to be cryptographically secure, just reasonably...
Filter dict to contain only certain keys?
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Constructing a new dict:
dict_you_want = { your_key: old_dict[your_key] for your_key in your_keys }
Uses dictionary comprehension.
If you use a version which lacks them (ie Python 2.6 and earlier), make it dict((your_key, old_dict[your_key]) for ...). It's the same, th...
Principal component analysis in Python
I'd like to use principal component analysis (PCA) for dimensionality reduction. Does numpy or scipy already have it, or do I have to roll my own using numpy.linalg.eigh ?
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How to get unique values in an array
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Since I went on about it in the comments for @Rocket's answer, I may as well provide an example that uses no libraries. This requires two new prototype functions, contains and unique
Array.prototype.contains = function(v) {
for (var i = 0; i < this.length; i++) {...
Python group by
... 2 steps. First, create a dictionary.
>>> input = [('11013331', 'KAT'), ('9085267', 'NOT'), ('5238761', 'ETH'), ('5349618', 'ETH'), ('11788544', 'NOT'), ('962142', 'ETH'), ('7795297', 'ETH'), ('7341464', 'ETH'), ('9843236', 'KAT'), ('5594916', 'ETH'), ('1550003', 'ETH')]
>>> from ...
Plot yerr/xerr as shaded region rather than error bars
...size=y.shape)
y += np.random.normal(0, 0.1, size=y.shape)
plt.plot(x, y, 'k-')
plt.fill_between(x, y-error, y+error)
plt.show()
See also the matplotlib examples.
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improve this answer
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Clean ways to write multiple 'for' loops
...gt; myData;
public:
// ...
int& operator()( int i, int j, int k )
{
return myData[ ((i * y) + j) * z + k ];
}
};
Or if you want to index using [][][], you need an operator[]
which returns a proxy.
Once you've done this, if you find that you constantly have to
iterate ...