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Sort rows in data.table in decreasing order on string key `order(-x,v)` gives error on data.table 1.
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Update
data.table v1.9.6+ now supports OP's original attempt and the following answer is no longer necessary.
You can use DT[order(-rank(x), y)].
x y v
1: c 1 7
2: c 3 8
3: c 6 9
4: b 1 1
5: b 3 2
6: b 6 3
7: a 1 4
8: a 3 5
9: a 6 6
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Test whether string is a valid integer
...l script. If the user provided a valid integer, the script does one thing, and if not valid, it does something else. Trouble is, I haven't found an easy (and reasonably elegant) way of doing this - I don't want to have to pick it apart char by char.
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Correct way to detach from a container without stopping it
...ctional OS. When you run a container the process you launch take the PID 1 and assume init power. So when that process is terminated the daemon stop the container until a new process is launched (via docker start) (More explanation on the matter http://phusion.github.io/baseimage-docker/#intro)
If ...
Finding what methods a Python object has
...t an AttributeError, you can use this instead:
getattr( is intolerant of pandas style python3.6 abstract virtual sub-classes. This code does the same as above and ignores exceptions.
import pandas as pd
df = pd.DataFrame([[10, 20, 30], [100, 200, 300]],
columns=['foo', 'bar',...
MySQL error code: 1175 during UPDATE in MySQL Workbench
...update the column visited to give it the value 1. I use MySQL workbench, and I'm writing the statement in the SQL editor from inside the workbench. I'm writing the following command:
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throwing an exception in objective-c/cocoa
...xception exceptionWith…]) syntax, the parser recognizes that as an exit and does not display the warning.
– mattorb
Aug 27 '11 at 16:32
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How do I get the SharedPreferences from a PreferenceActivity in Android?
...plication. I am inflating the settings via a xml file so that my onCreate (and complete class methods) looks like this:
7 ...
How do I check if a variable exists in a list in BASH
...amp; echo 'yes' || echo 'no'. it's correct assuming space is the separator and $x doesn't contain space
– Tianren Liu
Apr 5 '16 at 21:47
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How can I configure the font size for the tree item in the package explorer in Eclipse?
..., there was no way in Eclipse to change the font used for Package Explorer and other such views. You can only change the font for editor views. This is a policy decision on the part of the Eclipse developers (see, e.g., bugs 49548, 202091). (Grumble.) The font used is the one set by the general look...
How to display all methods of an object?
...r(function (p) {
return typeof Math[p] === 'function';
}));
//-> ["random", "abs", "acos", "asin", "atan", "ceil", "cos", "exp", ...etc ]
In ES3 browsers (IE 8 and lower), the properties of built-in objects aren't enumerable. Objects like window and document aren't built-in, they're defi...