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How do I determine k when using k-means clustering?
I've been studying about k-means clustering , and one thing that's not clear is how you choose the value of k. Is it just a matter of trial and error, or is there more to it?
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Is calculating an MD5 hash less CPU intensive than SHA family functions?
...ond, for a "long" message (this is what you get for messages longer than 8 kB). This is with sphlib, a library of hash function implementations in C (and Java). All implementations are from the same author (me) and were made with comparable efforts at optimizations; thus the speed differences can be...
How to replace a hash key with another key
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hash[:new_key] = hash.delete :old_key
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transform object to array with lodash
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What about if you wanted to preserve the key as a property? (in this example, if the id property did not exist and you wanted to create it based on the key of each object.
– Michael Liquori
Mar 7 '16 at 20:02
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How to elegantly rename all keys in a hash in Ruby? [duplicate]
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ages = { 'Bruce' => 32, 'Clark' => 28 }
mappings = { 'Bruce' => 'Bruce Wayne', 'Clark' => 'Clark Kent' }
ages.transform_keys(&mappings.method(:[]))
#=> { 'Bruce Wayne' => 32, 'Clark Kent' => 28 }
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Removing duplicates from a list of lists
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>>> k = [[1, 2], [4], [5, 6, 2], [1, 2], [3], [4]]
>>> import itertools
>>> k.sort()
>>> list(k for k,_ in itertools.groupby(k))
[[1, 2], [3], [4], [5, 6, 2]]
itertools often offers the fastest and mo...
Extract subset of key-value pairs from Python dictionary object?
I have a big dictionary object that has several key value pairs (about 16), but I am only interested in 3 of them. What is the best way (shortest/efficient/most elegant) to achieve that?
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Sort Go map values by keys
... through the returned map in the code, returned by the topic function, the keys are not appearing in order.
6 Answers
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Elegant way to invert a map in Scala
...ning Scala currently and needed to invert a Map to do some inverted value->key lookups. I was looking for a simple way to do this, but came up with only:
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Check if at least two out of three booleans are true
An interviewer recently asked me this question: given three boolean variables, a, b, and c, return true if at least two out of the three are true.
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