51
votes
21
answers
735
views
Is there a standard sign function (signum, sgn) in C/C++?
I want a function that returns -1 for negative numbers and +1 for positive numbers. http://en.wikipedia.org/wi
62
votes
12
answers
2.4K
views
JavaScript math, round to two decimal places
I have the following JavaScript syntax: var discount = Math.round(100 - (price / listprice) * 100)
63
votes
26
answers
2.7K
views
How to check if a number is a power of 2
Today I needed a simple algorithm for checking if a number is a power of 2. The algorithm needs to be: Simpl
56
votes
30
answers
793
views
Divide a number by 3 without using *, /, +, -, % operators
How would you divide a number by 3 without using *, /, +, -, %, operators? The number may be signed or unsig
57
votes
6
answers
2.2K
views
How do I determine whether my calculation of pi is accurate?
I was trying various methods to implement a program that gives the digits of pi sequentially. I tried the Tayl
61
votes
28
answers
1.6K
views
Understanding "randomness"
I can't get my head around this, which is more random? rand() OR: rand() * rand() I´m finding it a
67
votes
21
answers
1.8K
views
What is JavaScript's highest integer value that a number can go to without losing precision?
Is this defined by the language? Is there a defined maximum? Is it different in different browsers?
52
votes
18
answers
1.7K
views
How to perform an integer division, and separately get the remainder, in JavaScript?
In JavaScript, how do I get: The whole number of times a given integer goes into another? The remainder?
56
votes
30
answers
436
views
Determine Whether Two Date Ranges Overlap
Given two date ranges, what is the simplest or most efficient way to determine whether the two date ranges ove
55
votes
30
answers
1K
views
Fastest way to determine if an integer's square root is an integer
I'm looking for the fastest way to determine if a long value is a perfect square (i.e. its square root is
61
votes
30
answers
1.4K
views
Is floating point math broken?
Consider the following code: 0.1 + 0.2 == 0.3 -> false 0.1 + 0.2 -> 0.30000000000000004
54
votes
4
answers
2.4K
views
Is there an R function for finding the index of an element in a vector?
In R, I have an element x and a vector v. I want to find the first index of an element in v that is equal to x
54
votes
6
answers
2.5K
views
How to find the length of a string in R
How to find the length of a string (number of characters in a string) without splitting it in R? I know how to
60
votes
15
answers
1.8K
views
How can I trim leading and trailing white space?
I am having some troubles with leading and trailing white space in a data.frame. For example, I like to take a
64
votes
29
answers
2.6K
views
Elegant way to check for missing packages and install them?
I seem to be sharing a lot of code with coauthors these days. Many of them are novice/intermediate R users and
54
votes
12
answers
1.9K
views
How can two strings be concatenated?
How can I concatenate (merge, combine) two values? For example I have: tmp = cbind("GAD", "AB") tmp # [,
61
votes
6
answers
1.9K
views
How do I install an R package from source?
A friend sent me along this great tutorial on webscraping NYtimes with R. I would really love to try it. Howev
52
votes
5
answers
2.7K
views
How to write trycatch in R
I want to write trycatch code to deal with error in downloading from the web. url <- c( "http://stat.e
57
votes
30
answers
2.1K
views
How to find the statistical mode?
In R, mean() and median() are standard functions which do what you'd expect. mode() tells you the intern
57
votes
20
answers
1.6K
views
Counting the number of elements with the values of x in a vector
I have a vector of numbers: numbers <- c(4,23,4,23,5,43,54,56,657,67,67,435, 453,435,324,34,456,5
