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javascript set a variable if undefined
...f the variable is strictly undefined then the safest way is to write:
var x = (typeof x === 'undefined') ? your_default_value : x;
On newer browsers it's actually safe to write:
var x = (x === undefined) ? your_default_value : x;
but be aware that it is possible to subvert this on older browse...
Convert Int to String in Swift
...
Converting Int to String:
let x : Int = 42
var myString = String(x)
And the other way around - converting String to Int:
let myString : String = "42"
let x: Int? = myString.toInt()
if (x != nil) {
// Successfully converted String to Int
}
Or if ...
Why are regular expressions so controversial? [closed]
When exploring regular expressions (otherwise known as RegEx-es), there are many individuals who seem to see regular expressions as the Holy Grail. Something that looks so complicated - just must be the answer to any question. They tend to think that every problem is solvable using regular express...
How to avoid warning when introducing NAs by coercion
...
Use suppressWarnings():
suppressWarnings(as.numeric(c("1", "2", "X")))
[1] 1 2 NA
This suppresses warnings.
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Best practices for circular shift (rotate) operations in C++
...otate question with some more details about what asm gcc/clang produce for x86.
The most compiler-friendly way to express a rotate in C and C++ that avoids any Undefined Behaviour seems to be John Regehr's implementation. I've adapted it to rotate by the width of the type (using fixed-width types ...
In php, is 0 treated as empty?
Code will explain more:
18 Answers
18
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Drop data frame columns by name
...
You can use a simple list of names :
DF <- data.frame(
x=1:10,
y=10:1,
z=rep(5,10),
a=11:20
)
drops <- c("x","z")
DF[ , !(names(DF) %in% drops)]
Or, alternatively, you can make a list of those to keep and refer to them by name :
keeps <- c("y", "a")
DF[keeps]
EDI...
pyplot axes labels for subplots
...hen set the common labels.
import random
import matplotlib.pyplot as plt
x = range(1, 101)
y1 = [random.randint(1, 100) for _ in xrange(len(x))]
y2 = [random.randint(1, 100) for _ in xrange(len(x))]
fig = plt.figure()
ax = fig.add_subplot(111) # The big subplot
ax1 = fig.add_subplot(211)
ax2 =...
Tricks to manage the available memory in an R session
...em. But by far the most effective solution was ... to run under 64-bit Linux with ample memory.
27 Answers
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