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How do I determine k when using k-means clustering?
... clear is how you choose the value of k. Is it just a matter of trial and error, or is there more to it?
19 Answers
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Understanding the map function
...your function should look for None and handle them, otherwise you will get errors. In Python 3 map() will stop after finishing with the shortest list. Also, in Python 3, map() returns an iterator, not a list.
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Useful code which uses reduce()? [closed]
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answered Jul 17 '10 at 17:05
ssolerssoler
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Set every cell in matrix to 0 if that row or column contains a 0
... row and column are both 1s.
Coding it will be tricky to avoid off-by-one errors etc but it should work in one pass.
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Find index of last occurrence of a substring in a string
... recent call last):
File "<stdin>", line 1, in <module>
ValueError: substring not found
The difference is when the substring is not found, rfind() returns -1 while rindex() raises an exception ValueError (Python2 link: ValueError).
If you do not want to check the rfind() return cod...
Programmatically retrieve memory usage on iPhone
...iB): %f", ((CGFloat)info.resident_size / 1048576));
} else {
NSLog(@"Error with task_info(): %s", mach_error_string(kerr));
}
}
There is also a field in the structure info.virtual_size which will give you the number of bytes available virtual memory (or memory allocated to your application...
How do I list one filename per output line in Linux?
... -1 ftw.
– crantok
May 21 '13 at 21:05
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ls defaults to -1 behavior when the output isn't connect...
In pure functional languages, is there an algorithm to get the inverse function?
... "chase" a solution while we explore a design space using "undefined" and "error" during development). A "bottom" x has the type a. It "inhabits" (or is a "value") of every type. This is a logical contradiction, since types are propositions and there is no value which satisfies every proposition....
SQL Query to concatenate column values from multiple rows in Oracle
...ted string exceeds 4000 characters( limit for VARCHAR2 in SQL ), the below error is thrown, which is difficult to manage in Oracle versions upto 12.1
ORA-01489: result of string concatenation is too long
A new feature added in 12cR2 is the ON OVERFLOW clause of LISTAGG.
The query including t...
How to convert a string to lower case in Bash?
...sn't work for me (GNU bash version 4.2.46 and 4.0.33 (and same behaviour 2.05b.0 but nocasematch is not implemented)) even with using shopt -u nocasematch;. Unsetting that nocasematch causes [[ "fooBaR" == "FOObar" ]] to match OK BUT inside case weirdly [b-z] are incorrectly matched by [A-Z]. Bash i...