大约有 10,150 项符合查询结果（耗时：0.0454秒） [XML]
Mean per group in a data.frame [duplicate]
I have a data.frame and I need to calculate the mean per group (i.e. per Month , below).
8 Answers
...
How do you use the Immediate Window in Visual Studio?
The Immediate Window is an immensely useful tool for debugging applications. It can be used to execute code statements that are valid in the context of a break point and inspect values. I also use it to type code snippets to learn language features.
...
How to see if an NSString starts with a certain other string?
I am trying to check to see if a string that I am going to use as URL starts with http. The way I am trying to check right now doesn't seem to be working. Here is my code:
...
What is the result of % in Python?
What does the % in a calculation? I can't seem to work out what it does.
19 Answers
...
Argparse optional positional arguments?
I have a script which is meant to be used like this:
usage: installer.py dir [-h] [-v]
3 Answers
...
How to create a temporary directory?
I use to create a tempfile , delete it and recreate it as a directory:
4 Answers
4
...
Is there a way to provide named parameters in a function call in JavaScript?
I find the named parameters feature in C# quite useful in some cases.
10 Answers
10
...
HashMap get/put complexity
We are used to saying that HashMap get/put operations are O(1). However it depends on the hash implementation. The default object hash is actually the internal address in the JVM heap. Are we sure it is good enough to claim that the get/put are O(1) ?
...
What is Weak Head Normal Form?
What does Weak Head Normal Form (WHNF) mean? What does Head Normal form (HNF) and Normal Form (NF) mean?
6 Answers
...
Error handling in C code
What do you consider "best practice" when it comes to error handling errors in a consistent way in a C library.
22 Answers
...