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How to rename a single column in a data.frame?
...r.name'
This code pretty much does the following:
names(df) looks into all the names in the df
[names(df) == old.var.name] extracts the variable name you want to check
<- 'new.var.name' assigns the new variable name.
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When to use a linked list over an array/array list?
...you know the number of elements in the array ahead of time so that you can allocate the correct amount of memory for the array
you need speed when iterating through all the elements in sequence. You can use pointer math on the array to access each element, whereas you need to lookup the node based...
Why is semicolon allowed in this python snippet?
...ot warrant the use of semicolons to end statements.
So why is this (below) allowed?
15 Answers
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What is The Rule of Three?
...in various contexts,
and we should understand what "copying an object" actually means.
Let us consider a simple example:
class person
{
std::string name;
int age;
public:
person(const std::string& name, int age) : name(name), age(age)
{
}
};
int main()
{
person a("Bjar...
How to retrieve absolute path given relative
...
use:
find "$(pwd)"/ -type f
to get all files or
echo "$(pwd)/$line"
to display full path (if relative path matters to)
share
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improve this answer
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Count number of days between two dates
...t's most likely the dates are coming from ActiveRecord which will automatically cast them to date objects. The given text is identical to Date object representation as well, making it highly likely it's come from a native source.
– Andrew France
Mar 5 '12 at 20...
Error 908: Permission RECEIVE_SMS has been denied. - App Inventor 2 中...
...发送短信/拨打电话，我们创建了SendMessageDirect和MakePhoneCallDirect模块，执行旧的需要额外权限的行为。我们选择让现有的SendMessage和MakePhoneCall模块通过Intents启动默认应用程序，这是Google政策推荐的做法，对大多数人应该有效。
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Checking for NULL pointer in C/C++ [closed]
In a recent code review, a contributor is trying to enforce that all NULL checks on pointers be performed in the following manner:
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What is this 'Lambda' everyone keeps speaking of?
... 'Lambda' everyone keeps speaking of? A lot of people seem to love it, but all I can gather from it is it is just a way of cramming lots of lines of code into a single expression.
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C++ compiling on Windows and Linux: ifdef switch [duplicate]
... @MestreLion The Predef project has since been absorbed into Boost, but all the macros are still listed in the documentation here: boost.org/doc/libs/release/libs/predef/doc/html/index.html
– rubenvb
Mar 26 '16 at 12:43
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