大约有 48,000 项符合查询结果（耗时：0.0910秒） [XML]
Assign multiple columns using := in data.table, by group
...b col1 col2
# 1: 1 1 hi hello
# 2: 2 2 hi hello
# 3: 3 3 hi hello
# 4: 1 4 hi hello
# 5: 2 5 hi hello
# 6: 3 6 hi hello
x[ , c("mean", "sum") := list(mean(b), sum(b)), by = a][]
# a b col1 col2 mean sum
# 1: 1 1 hi hello 2.5 5
# 2: 2 2 hi hello 3.5 7
# 3: 3 3 hi hello ...
Asterisk in function call
...rguments in the function call.
So if uniqueCrossTabs was [ [ 1, 2 ], [ 3, 4 ] ], then itertools.chain(*uniqueCrossTabs) is the same as saying itertools.chain([ 1, 2 ], [ 3, 4 ])
This is obviously different from passing in just uniqueCrossTabs. In your case, you have a list of lists that you wish t...
How to convert byte array to Bitmap
... manfcas
1,83566 gold badges2828 silver badges4545 bronze badges
answered Oct 1 '11 at 13:41
UttamUttam
11.6k33 gold badges2...
Why does [5,6,8,7][1,2] = 8 in JavaScript?
...
[1,2,3,4,5,6][1,2,3];
^ ^
| |
array + — array subscript access operation,
where index is `1,2,3`,
which is an expression that evaluates to `3`.
The se...
How can I strip the whitespace from Pandas DataFrame headers?
...
Erfan
27k55 gold badges2525 silver badges4646 bronze badges
answered Feb 6 '14 at 15:49
TomAugspurgerTomAugspurger
21.4...
Why does substring slicing with index out of range work?
...
You're correct! 'example'[3:4] and 'example'[3] are fundamentally different, and slicing outside the bounds of a sequence (at least for built-ins) doesn't cause an error.
It might be surprising at first, but it makes sense when you think about it. Ind...
How can you sort an array without mutating the original array?
...
answered Feb 24 '17 at 15:52
Putzi SanPutzi San
2,38011 gold badge1414 silver badges2626 bronze badges
...
How do I get cURL to not show the progress bar?
...
answered Sep 10 '11 at 19:04
unutbuunutbu
665k138138 gold badges14831483 silver badges14721472 bronze badges
...
Is there a literal notation for an array of symbols?
... Phil Ross
22.5k99 gold badges6666 silver badges7474 bronze badges
answered Jan 25 '13 at 23:52
David GraysonDavid Grayson
68k2...
Is \d not supported by grep's basic expressions?
...
rogerdpack
46.3k3030 gold badges200200 silver badges315315 bronze badges
answered Aug 1 '11 at 16:08
DaenythDaen...