大约有 40,000 项符合查询结果（耗时：0.0497秒） [XML]
Mean per group in a data.frame [duplicate]
...
This type of operation is exactly what 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 ...
How do I delete unpushed git commits?
...ch the exact branch that you have in the origin.
git reset --hard origin/<branch>
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ExecutorService, how to wait for all tasks to finish
...parlance, you'll need to modify or wrap ComputeDTask to implement Callable<>, which can give you quite a bit more flexibility. Probably in your app there is a meaningful implementation of Callable.call(), but here's a way to wrap it if not using Executors.callable().
ExecutorService es = Exe...
Mixing C# & VB In The Same Project
...iles to 1 assembly usually) has to be one language. However, you can use multiple assemblies, and each can be coded in a different language because they are all compiled to CIL.
It compiled fine and didn't complain because a VB.NET project will only actually compile the .vb files and a C# project wi...
In Python, how do I split a string and keep the separators?
...the text of all groups in the pattern are also returned as part of the resulting list."
– Vinay Sajip
Jan 25 '10 at 23:54
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Sort objects in ArrayList by date?
...our object comparable:
public static class MyObject implements Comparable<MyObject> {
private Date dateTime;
public Date getDateTime() {
return dateTime;
}
public void setDateTime(Date datetime) {
this.dateTime = datetime;
}
@Override
public int compareTo(MyObject o)...
Adding additional data to select options using jQuery
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HTML Markup
<select id="select">
<option value="1" data-foo="dogs">this</option>
<option value="2" data-foo="cats">that</option>
<option value="3" data-foo="gerbils">other</option>
</sele...
Filter Java Stream to 1 and only 1 element
... want to guarantee, however, that there is one and only one match to the filter criteria.
20 Answers
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How to check for the type of a template parameter?
...
Use is_same:
#include <type_traits>
template <typename T>
void foo()
{
if (std::is_same<T, animal>::value) { /* ... */ } // optimizable...
}
Usually, that's a totally unworkable design, though, and you really want to speci...
ReadOnlyCollection or IEnumerable for exposing member collections?
...all this member and you guarantee that no code will ever use:
ICollection<Foo> evil = (ICollection<Foo>) bar.Foos;
evil.Add(...);
then sure, no harm will be done if you just return the collection directly. I generally try to be a bit more paranoid than that though.
Likewise, as you s...