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Assign multiple columns using := in data.table, by group
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This now works in v1.8.3 on R-Forge. Thanks for highlighting it!
x <- data.table(a = 1:3, b = 1:6)
f <- function(x) {list("hi", "hello")}
x[ , c("col1", "col2") := f(), by = a][]
# a b col1 col2
# 1: 1 1 hi hello
# ...
How to replace a character with a newline in Emacs?
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It's really a good idea for the characters which I don't know the key bind.
– Lei
Mar 5 '09 at 18:16
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Why aren't my breakpoints working?
...ion went along these lines: "come on, please, you really think I wouldn't know better...... oh.")
Make sure you haven't accidentally set "Active Build Configuration" to "Release."
Under "Targets" in the graphical tree display of your project, right click on your Target and do "Get Info." Look fo...
Can you list the keyword arguments a function receives?
...argspec(func)
(['a', 'b', 'c'], 'args', 'kwargs', (42,))
If you want to know if its callable with a particular set of args, you need the args without a default already specified. These can be got by:
def getRequiredArgs(func):
args, varargs, varkw, defaults = inspect.getargspec(func)
if ...
An error occurred while validating. HRESULT = '8000000A'
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This is a known issue in Visual Studio 2010 (a race condition). See this connect item.
We've run into this as well, and had a very unsatisfying support call on this issue with Microsoft. Long story short: it's a known issue, it won't b...
Hidden features of Android development?
...st yet in the Hidden Features series that I've been tracking for a while now.
6 Answers
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.htaccess mod_rewrite - how to exclude directory from rewrite rule
...ectories on my server from these rules, so they can become accessible. For now all requests are sent to index.php file.
6 ...
Why does the order in which libraries are linked sometimes cause errors in GCC?
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(See the history on this answer to get the more elaborate text, but I now think it's easier for the reader to see real command lines).
Common files shared by all below commands
$ cat a.cpp
extern int a;
int main() {
return a;
}
$ cat b.cpp
extern int b;
int a = b;
$ cat d.cpp
int b;
L...
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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An item with the same key has already been added
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Would someone know how to identify which is "the same key?"
– ClayKaboom
Apr 15 '14 at 18:34
1
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