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What does .SD stand for in data.table in R

...ks useful but I do not really know what I am doing with it. What does it stand for? Why is there a preceding period (full stop). What is happening when I use it? ...
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CASCADE DELETE just once

... with the ON DELETE CASCADE rule. Is there any way I can perform a delete and tell Postgresql to cascade it just this once? Something equivalent to ...
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Are tuples more efficient than lists in Python?

Is there any performance difference between tuples and lists when it comes to instantiation and retrieval of elements? 8 A...
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Importing a Maven project into Eclipse from Git

How can I get the effect of choosing to import from both Maven and Git and have Eclipse properly generate my project? 13 A...
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How to skip over an element in .map()?

...tion would have kept it. update — This question gets a lot of attention, and I'd like to add the following clarifying remark. The purpose of .map(), as a concept, is to do exactly what "map" means: transform a list of values into another list of values according to certain rules. Just as a paper m...
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What does the number in parentheses shown after Unix command names in manpages mean?

... It's the section that the man page for the command is assigned to. These are split as General commands System calls C library functions Special files (usually devices, those found in /dev) and drivers File formats and conventions Games and screensavers Miscellanea Sys...
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Java 7 language features with Android

Just wondering if anyone has tried using new Java 7 language features with Android? I know that Android reads the bytecode that Java spits out and turns it to dex. So I guess my question is can it understand the bytecode of Java 7? ...
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Unable to copy file - access to the path is denied

... I solved this problem by deleting the contentious files from bin folder and rebuilding the project. share | improve this answer | follow | ...
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Detect IF hovering over element with jQuery

... Original (And Correct) Answer: You can use is() and check for the selector :hover. var isHovered = $('#elem').is(":hover"); // returns true or false Example: http://jsfiddle.net/Meligy/2kyaJ/3/ (This only works when the selector m...
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Meaning of $? (dollar question mark) in shell scripts

... This is the exit status of the last executed command. For example the command true always returns a status of 0 and false always returns a status of 1: true echo $? # echoes 0 false echo $? # echoes 1 From the manual: (acessible by calling man bash in your shell) $?...