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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...
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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...
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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...
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Filter dict to contain only certain keys?

... 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...
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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

... 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++) {...
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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 ...
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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. share | 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 ...