Rand

A javascript class which provides random numbers with different distributions

Download

Please download rand.min.js or rand.js.

Usage

// Get a random number between 0 and 10 with "double exponential"
// distribution (ex. 0.4623468576464802)
Rand.random(0, 10, 'double-exponential');

This is a distribution that has a high probability in the middle and then "dies out" in both directions.

To use the normal random function, use the random or constant distribution

// Just a random number between 0 and 1 (ex. 0.3653468576464802)
Rand.random();

// Same as
Rand.random(0, 1, 'constant');

Choose another random generator

The library uses Math.random as default random number generator. But any function generating a decimal value between 0 and 1 can be used. To overwrite the default random generator write the following:

Rand.randomGenerator = anotherRandomNumberGenerator;

Random values

Boolean

// Get a boolean value (true or false)
Rand.bool();

// Get a boolean value with a 60% probability of beeing true
Rand.bool(0.6);

Integer

// A random integer between 0 and 1, ah yeah! (ex. 1 or 0)
Rand.int();

// A random integer between 0 and 26 (ex. 13)
Rand.int(0, 26);

// Use a different probability distribution (ex. 13)
Rand.in(0, 26, 'double-exponent');

Hashes

// A random hash with 40 hexadecimal chars (0-f) (ex. "c3d0b51b42205d039e0a06e1f221d2f742aa59c1")
Rand.hash();

// Random hash with a length of 32 chars (ex. "f5495b546aa984a74a2cc45f08917147")
Rand.hash(32);

Base 64

Hash with lowercase, uppercase, numbers and +/

// A base64 encoded hash, 40 chars long (ex. "DbVUCEY5cTu9Tb9eMmWjuioKqM/bEUrMsR5rPjea")
Rand.base64();

// Or defined length (64 chars long)
// (ex. "IfgBO2And5NnhDkC4l97ZyUWZI8/WEMqCv+mn/DFFurEsETYLihLK8plT4ni237A")
Rand.base64(64);

Base 36

Hash with lowercase and numbers

// Random base36 encoded hash, 40 chars long (ex. "n0f4612gxtzi8z3w8fusgo12ihycnpcq711f134z")
Rand.base36();

// Or defined length (86 chars long)
// (ex. "1nrrb10whkwz1i38he91iqh0wylv1x0xn1tk1jy1na2561w21201kv951eg1ui29u1p0mrkjdk1v5j5289paf6")
Rand.base36(86);

Date

// A random date between now and 1 year from now (ex. Thu Apr 03 2014 16:38:14 GMT+0200 (CEST))
Rand.date();

// A random date between two dates
Rand.date(new Date('2013-05-12'), new Date('2014-02-21'));

Choose from array

You can make Rand choose a value from an array

// Pick random item from array (ex. 'blue')
Rand.choose(['red', 'green', 'blue', 'orange', 'pink']);

// Choose with a different distribution, (ex. 'red' most of the times)
Rand.choose(['red', 'green', 'blue', 'orange', 'pink'], 'exponential')

// If you provide an empty array the function will return null
Rand.choose([]); // null

// Or even
Rand.choose(); // null

Colors

// A random hexadecimal color (ex. "#7e39b5")
Rand.color();

// A random rgba color (ex. "rgba(196,234,50,0.16)")
Rand.rgba();

Other stuff

// Random character (ex. 'a')
Rand.char();

Distributions

The Rand library has some build in distributions that you can use in some functions, for example Rand.random(min, max, distribution).

Use a string identifier for the distribution, default is random which is random over the whole range.

Rand.random(0, 1, 'random');

The distributions are shown in histograms below, meaning that the graphs represents the probability of x in 10 million runs. For example the double-exponential distibution where 0.5 has the highest probability of about 1.6%.

Normal

The normal distribution has a bump in the middle, used a lot!

To use the normal distribution like so:

Rand.random(0, 1, 'normal');

Double exponential

The double-exponential or stable distribution has a sharp edge at 0-1 (middle of range, if you use Rand.random(0, 10) then the edge will be at 5) and then dies out exponential in both directions

To use this distribution use double-exponential or stable like so:

Rand.random(0, 1, 'double-exponential');

Exponential

The exponential distribution dies out exponantially in one direction

To use this distribution use exponential like so:

Rand.random(0, 1, 'exponential');

Survival

The survival distribution is much like the exponential one, excep survival has another "tail"

To use this distribution use survival like so:

Rand.random(0, 1, 'survival');

Linear

Rand has 2 linear distributions, linear-increase and linear-decrease.

The linear-increase looks like this

And linear-decrease looks like this

To use these distributions use linear-increase or linear-decrease like so:

Rand.random(0, 1, 'linear-increase');
Rand.random(0, 1, 'linear-decrease');