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Assign multiple columns using := in data.table, by group
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162
This now works in v1.8.3 on R-Forge. Thanks for highlighting it!
x <- data.table(a = 1:3, ...
What does this square bracket and parenthesis bracket notation mean [first1,last1)?
I have seen number ranges represented as [first1,last1) and [first2,last2) .
4 Answers
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Logical operators for boolean indexing in Pandas
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219
When you say
(a['x']==1) and (a['y']==10)
You are implicitly asking Python to convert (a['x'...
Why does auto a=1; compile in C?
...d d; // actually unsigned int
which is still common in modern code.
C++11 reused the keyword, which few if any C++ programmers were using with the original meaning, for its type inference. This is mostly safe because the "everything is int" rule from C had already been dropped in C++98; the only...
What does “@@ -1 +1 @@” mean in Git's diff output?
...to-file to-file-modification-time
The time stamp looks like 2002-02-21 23:30:39.942229878 -0800 to indicate the date, time with fractional seconds, and time zone. The fractional seconds are omitted on hosts that do not support fractional time stamps.
You can change the header's content wi...
How to get the anchor from the URL using jQuery?
...se the .indexOf() and .substring(), like this:
var url = "www.aaa.com/task1/1.3.html#a_1";
var hash = url.substring(url.indexOf("#")+1);
You can give it a try here, if it may not have a # in it, do an if(url.indexOf("#") != -1) check like this:
var url = "www.aaa.com/task1/1.3.html#a_1", idx = u...
Mean per group in a data.frame [duplicate]
...aggregate was designed for:
d <- read.table(text=
'Name Month Rate1 Rate2
Aira 1 12 23
Aira 2 18 73
Aira 3 19 45
Ben 1 53 19
Ben 2 22 87
Ben 3 19 45
Cat 1 22 ...
Python Dictionary Comprehension
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>>> d = {n: n**2 for n in range(5)}
>>> print d
{0: 0, 1: 1, 2: 4, 3: 9, 4: 16}
If you want to set them all to True:
>>> d = {n: True for n in range(5)}
>>> print d
{0: True, 1: True, 2: True, 3: True, 4: True}
What you seem to be asking for is a way to set...
In Matlab, when is it optimal to use bsxfun?
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152
+500
There ...
Ruby: What is the easiest way to remove the first element from an array?
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11 Answers
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