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How can the Euclidean distance be calculated with NumPy?
...roduction to Data Mining
This works because Euclidean distance is l2 norm and the default value of ord parameter in numpy.linalg.norm is 2.
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How can I remove the first line of a text file using bash/sed script?
...you the last 5 lines of the input. The + sign kind of inverts the argument and make tail print anything but the first x-1 lines. tail -n +1 would print the whole file, tail -n +2 everything but the first line, etc.
GNU tail is much faster than sed. tail is also available on BSD and the -n +2 flag i...
Why is iterating through a large Django QuerySet consuming massive amounts of memory?
...QuerySet in the following ways:
Iteration. A QuerySet is iterable, and it executes its database query the first time you iterate over it. For example, this will print the headline of all entries in the database:
for e in Entry.objects.all():
print e.headline
So your ten million ro...
Why is an array not assignable to Iterable?
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Arrays can implement interfaces (Cloneable and java.io.Serializable). So why not Iterable? I guess Iterable forces adding an iterator method, and arrays don't implement methods. char[] doesn't even override toString. Anyway, arrays of references should be considered l...
How do I make a batch file terminate upon encountering an error?
I have a batch file that's calling the same executable over and over with different parameters. How do I make it terminate immediately if one of the calls returns an error code of any level?
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quick random row selection in Postgres
... that contains couple of millions of rows. I have checked on the internet and I found the following
7 Answers
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How does the Comma Operator work
...itializers for symbol tables. Thus, it makes the following syntax possible and meaningful:
keywords = "and", "or", "not", "xor";
Notice that due to operator precedence, the code is (intentionally!) identical to
(((keywords = "and"), "or"), "not"), "xor";
That is, the first operator called is k...
C++ templates that accept only certain types
... class my_template<T*> {
...
};
// All other types are invalid, and will cause linker error messages.
[Minor EDIT 6/12/2013: Using a declared-but-not-defined template will result in linker, not compiler, error messages.]
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IOS7 : UIScrollView offset in UINavigationController
I'm currently migrating my app on ios 7 and I've been stuck for hours on the new navigationcontroller/bar management.
8 Ans...
Is there a Java equivalent or methodology for the typedef keyword in C++?
Coming from a C and C++ background, I found judicious use of typedef to be incredibly helpful. Do you know of a way to achieve similar functionality in Java, whether that be a Java mechanism, pattern, or some other effective way you have used?
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