大约有 47,000 项符合查询结果（耗时：0.0330秒） [XML]
Relative frequencies / proportions with dplyr
...se(n = n()) %>%
mutate(freq = n / sum(n))
# am gear n freq
# 1 0 3 15 0.7894737
# 2 0 4 4 0.2105263
# 3 1 4 8 0.6153846
# 4 1 5 5 0.3846154
From the dplyr vignette:
When you group by multiple variables, each summary peels off one level of the grouping. That mak...
Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_
...
10 Answers
10
Active
...
Static variables in member functions
...
169
Since class A is a non-template class and A::foo() is a non-template function. There will be o...
How to sort a list in Scala by two fields?
...
217
rows.sortBy(r => (r.lastName, r.firstName))
...
How can I make pandas dataframe column headers all lowercase?
...
180
You can do it like this:
data.columns = map(str.lower, data.columns)
or
data.columns = [x....
ObservableCollection not noticing when Item in it changes (even with INotifyPropertyChanged)
...
18 Answers
18
Active
...
OAuth: how to test with local URLs?
...
139
Update October 2016: Easiest now: use lvh.me which always points to 127.0.0.1.
Previous Answer...
Regex how to match an optional character
...
Use
[A-Z]?
to make the letter optional. {1} is redundant. (Of course you could also write [A-Z]{0,1} which would mean the same, but that's what the ? is there for.)
You could improve your regex to
^([0-9]{5})+\s+([A-Z]?)\s+([A-Z])([0-9]{3})([0-9]{3})([A-Z]{3})([A-...
What is :: (double colon) in Python when subscripting sequences?
...
10 Answers
10
Active
...
How to determine if a point is in a 2D triangle? [closed]
...nce issues.
And here's some code to get you started:
float sign (fPoint p1, fPoint p2, fPoint p3)
{
return (p1.x - p3.x) * (p2.y - p3.y) - (p2.x - p3.x) * (p1.y - p3.y);
}
bool PointInTriangle (fPoint pt, fPoint v1, fPoint v2, fPoint v3)
{
float d1, d2, d3;
bool has_neg, has_pos;
...