A tbl_df (pronounced tibble diff) is a variation of a data frame that is often used in tidyverse packages. It is implemented in the tibble package.
Use the as_data_frame function to turn a data frame into a tbl_df:
library(tibble)
mtcars_tbl <- as_data_frame(mtcars)
One of the most notable ...
C++11
inline namespace includes the content of the inlined namespace in the enclosing namespace, so
namespace Outer
{
inline namespace Inner
{
void foo();
}
}
is mostly equivalent to
namespace Outer
{
namespace Inner
{
void foo();
}
u...
let string1 = "Hello" //simple string
let string2 = "Line\nNewLine" //string with newline escape sequence
let string3 = @"Line\nSameLine" //use @ to create a verbatim string literal
let string4 = @"Line""with""quoutes inside" //dou...
Each enum class contains an implicit static method named values(). This method returns an array containing all values of that enum. You can use this method to iterate over the values. It is important to note however that this method returns a new array every time it is called.
public enum Day {
...
Lambda expressions can be used to handle events, which is useful when:
The handler is short.
The handler never needs to be unsubscribed.
A good situation in which a lambda event handler might be used is given below:
smtpClient.SendCompleted += (sender, args) => Console.WriteLine("Ema...
Django default project layout creates a single settings.py. This is often useful to split it like this:
myprojectroot/
myproject/
__init__.py
settings/
__init__.py
base.py
dev.py
prod.py
tests.py
This enables...
Assuming a class
from django.db import models
class Author(models.Model):
name = models.CharField(max_length=50)
def __str__(self):
return self.name
def get_absolute_url(self):
return reverse('view_author', args=[str(self.id)])
class Book(models.Mo...
tl;dr : Create a base class that defines two user objects (say user and another_user). Create your other models and define three Client instances.
self.client : Representing user logged in browser
self.another_client : Representing another_user 's client
self.unlogged_client : Representing unlo...
Filters are a special type of function that can modify how something is printed out to the page, or can be used to filter an array, or a ng-repeat action. You can create a filter by calling the app.filter() method, passing it a name and a function. See the examples below for details on syntax.
Fo...
To run a container interactively, pass in the -it options:
$ docker run -it ubuntu:14.04 bash
root@8ef2356d919a:/# echo hi
hi
root@8ef2356d919a:/#
-i keeps STDIN open, while -t allocates a pseudo-TTY.
package main
import (
"log"
"text/template"
"os"
)
type Person struct{
MyName string
MyAge int
}
var myTempContents string= `
This person's name is : {{.MyName}}
And he is {{.MyAge}} years old.
`
func main() {
t,err := temp...
To assign variables from the command-line, -v can be used:
$ awk -v myvar="hello" 'BEGIN {print myvar}'
hello
Note that there are no spaces around the equal sign.
This allows to use shell variables:
$ shell_var="hello"
$ awk -v myvar="$shell_var" 'BEGIN {print m...
Rcpp features two functions that enable code compilation inline and exportation directly into R: cppFunction() and evalCpp(). A third function called sourceCpp() exists to read in C++ code in a separate file though can be used akin to cppFunction().
Below is an example of compiling a C++ function w...
Within C++, one can set different compilation flags using:
// [[Rcpp::plugins(name)]]
List of the built-in plugins:
// built-in C++11 plugin
// [[Rcpp::plugins(cpp11)]]
// built-in C++11 plugin for older g++ compiler
// [[Rcpp::plugins(cpp0x)]]
// built-in C++14 plugin for C++14 standa...
In some cases you may want to wrap a synchronous operation inside a promise to prevent repetition in code branches. Take this example:
if (result) { // if we already have a result
processResult(result); // process it
} else {
fetchResult().then(processResult);
}
The synchronous and async...
Cloning a huge repository (like a project with multiple years of history) might take a long time, or fail because of the amount of data to be transferred. In cases where you don't need to have the full history available, you can do a shallow clone:
git clone [repo_url] --depth 1
The above comman...
Similarly to the SimpleXML, you can use DOMDocument to parse XML from a string or from a XML file
1. From a string
$doc = new DOMDocument();
$doc->loadXML($string);
2. From a file
$doc = new DOMDocument();
$doc->load('books.xml');// use the actual file path. Absolute or relative
Exa...
a. Running multiple queries at same time
All queries in MySQL connection are done one after another. It means that if you want to do 10 queries and each query takes 2 seconds then it will take 20 seconds to complete whole execution. The solution is to create 10 connection and run each query in a di...
