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Mean per group in a data.frame [duplicate]

... the many ways to specify the variables to act on. Here, vars(-Month) says all variables except Month. share | improve this answer | follow | ...
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Why does int i = 1024 * 1024 * 1024 * 1024 compile without error?

... @WouterLievens, overflow is normally an "unusual" condition, if not an outright error condition. It is a result of finite-precision math, which most people are not intuitively expecting to happen when they do math. In some cases, like -1 + 1, it's harmless;...
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How can I use a DLL file from Python?

...hlapi32.dll") # Set up prototype and parameters for the desired function call. # HLLAPI hllApiProto = ctypes.WINFUNCTYPE ( ctypes.c_int, # Return type. ctypes.c_void_p, # Parameters 1 ... ctypes.c_void_p, ctypes.c_void_p, ctypes.c_void_p) # ... thru 4. hllApiParams = (...
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Doctrine - How to print out the real sql, not just the prepared statement?

...trine is not sending a "real SQL query" to the database server : it is actually using prepared statements, which means : Sending the statement, for it to be prepared (this is what is returned by $query->getSql()) And, then, sending the parameters (returned by $query->getParameters()) and exe...
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LINQ query on a DataTable

...s.Cast<DataRow>().Where(myRow => (int)myRow["RowNo"] == 1). Personally, I don't find the call to AsEnumerable() any more complicated than the call to Cast<DataRow>(). As far as I know, the performance is the same, so it's just a matter of preference. – Collin K ...
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Event binding on dynamically created elements?

I have a bit of code where I am looping through all the select boxes on a page and binding a .hover event to them to do a bit of twiddling with their width on mouse on/off . ...
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Why should hash functions use a prime number modulus?

... Usually a simple hash function works by taking the "component parts" of the input (characters in the case of a string), and multiplying them by the powers of some constant, and adding them together in some integer type. So for e...
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Can't open config file: /usr/local/ssl/openssl.cnf on Windows [duplicate]

... The solution is running this command: set OPENSSL_CONF=C:\OpenSSL-Win32\bin\openssl.cfg or set OPENSSL_CONF=[path-to-OpenSSL-install-dir]\bin\openssl.cfg in the command prompt before using openssl command. Let openssl know for sure where to find its .cfg file. Al...
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URL encoding in Android

... the post :) But I am facing a problem. If the url is already encoded partially, it is encoding the already encoded parts. What should I do? For example: dj-videos.us/Music/XclusiveSinGleTrack/320%20Kbps/… The %20 is coded to %2520 – berserk Jan 7 '14 at 7:17...
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Django template how to look up a dictionary value with a variable

...I find this easier to read and it avoids the need for special coding. I usually need the key and the value inside the loop anyway. share | improve this answer | follow ...