Difference between revisions of "random"

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(Fix description and examples)
m (Some wiki formatting)
 
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|r4= [[Number]] from 0 (included) to 1 (excluded)
 
|r4= [[Number]] from 0 (included) to 1 (excluded)
  
|x1= <code>_rNumber = [[random]] 1;</code>
+
|x1= <sqf>_rNumber = random 1;</sqf>
  
|x2= <code>_rNumber = [[random]] -10;</code>
+
|x2= <sqf>_rNumber = random -10;</sqf>
  
 
|x3= Generate a random position inside a circle (see also [[Example Code: Random Area Distribution]])
 
|x3= Generate a random position inside a circle (see also [[Example Code: Random Area Distribution]])
<code>_center [[getPos]] [_radius * [[sqrt]] [[random]] 1, [[random]] 360];</code>
+
<sqf>_center getPos [_radius * sqrt random 1, random 360];</sqf>
  
 
|x4= Select a random value from an array:
 
|x4= Select a random value from an array:
<code>_array = ["apples", "pears", "bananas", "M16"];
+
<sqf>_array = ["apples", "pears", "bananas", "M16"];
  
_random = _array [[select]] [[floor]] [[random]] [[count]] _array; {{cc|Before {{arma2}}}}
+
_random = _array select floor random count _array; // Before Arma 2
_random = _array [[call]] [[BIS_fnc_selectRandom]]; {{cc|Since {{arma2}}}}
+
_random = _array call BIS_fnc_selectRandom; // Since Arma 2
_random = [[selectRandom]] _array; {{cc|Since {{arma3}} v1.56}}</code>
+
_random = selectRandom _array; // Since Arma 3 v1.56</sqf>
  
|seealso= [[selectRandom]], [[selectRandomWeighted]]
+
|seealso= [[selectRandom]] [[selectRandomWeighted]]
 
}}
 
}}
  
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<dd class="note">
 
<dd class="note">
 
Random selections including negative numbers can be obtained via:
 
Random selections including negative numbers can be obtained via:
<code>_Xrnd = round(random 200) -100;</code>
+
<sqf>_Xrnd = round(random 200) -100;</sqf>
  
 
This will yield numbers between -100 and 100.
 
This will yield numbers between -100 and 100.
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* The number returned is unlikely to be a whole number.<br>
 
* The number returned is unlikely to be a whole number.<br>
 
To return a whole number use either '''[[round]]''', '''[[ceil]]''' or '''[[floor]]''' together with [[random]]:
 
To return a whole number use either '''[[round]]''', '''[[ceil]]''' or '''[[floor]]''' together with [[random]]:
<code>x = [[round]] ([[random]] 5) will return 0, 1, 2, 3, 4 or 5. (non-uniform distribution, 0 and 5 are half as likely to be selected than any of the other numbers)
+
<sqf>
x = [[floor]] ([[random]] 5) will return 0, 1, 2, 3 or 4.  (uniform distribution, all numbers have the same probability of being selected)
+
x = round (random 5) // will return 0, 1, 2, 3, 4 or 5. (non-uniform distribution, 0 and 5 are half as likely to be selected than any of the other numbers)
x = [[ceil]] ([[random]] 5) will return 0, 1, 2, 3, 4 or 5. (0 is very unlikely, but possible, as ceil 0 is 0)</code>
+
x = floor (random 5) // will return 0, 1, 2, 3 or 4.  (uniform distribution, all numbers have the same probability of being selected)
 +
x = ceil  (random 5) // will return 0, 1, 2, 3, 4 or 5. (0 is very unlikely, but possible, as ceil 0 is 0)
 +
</sqf>
 
</dd>
 
</dd>
  

Latest revision as of 16:39, 13 May 2022

Hover & click on the images for description

Description

Description:
Syntax 2's distribution
Syntax 1 generates a random floating point value
Syntax 2 generates a Gaussian Distribution[1]. It uses the same method as setTriggerTimeout command and is quite useful for e.g spawning loot, making more valuable items more rare
Syntax 3 generates a seed-based random number
Syntax 4 generates a seed-based random noise (not Perlin) texture based on provided seed and returning the value at supplied coordinates
Groups:
Math

Syntax 1

Syntax:
random x
Parameters:
x: Number
Return Value:
Number from 0 (included) to x (excluded)

Syntax 2

Syntax:
random [min, mid, max]
Parameters:
min: Number
mid: Number
max: Number
Return Value:
Number in range from min to max, weighted by mid

Syntax 3

Syntax:
seed random x
Parameters:
seed: Number - an integer. Any float value will be truncated (e.g -0.9, -0.1, 0.1 or 0.9 will be read as 0)
x: Number
Return Value:
Number from 0 (included) to x (excluded)

Syntax 4

Syntax:
seed random [x, y]
Parameters:
seed: Number
x: Number - x texture position
y: Number - y texture position
Return Value:
Number from 0 (included) to 1 (excluded)

Examples

Example 1:
_rNumber = random 1;
Example 2:
_rNumber = random -10;
Example 3:
Generate a random position inside a circle (see also Example Code: Random Area Distribution)
_center getPos [_radius * sqrt random 1, random 360];
Example 4:
Select a random value from an array:
_array = ["apples", "pears", "bananas", "M16"]; _random = _array select floor random count _array; // Before Arma 2 _random = _array call BIS_fnc_selectRandom; // Since Arma 2 _random = selectRandom _array; // Since Arma 3 v1.56

Additional Information

See also:
selectRandom selectRandomWeighted

Notes

Report bugs on the Feedback Tracker and/or discuss them on the Arma Discord or on the Forums.
Only post proven facts here! Add Note
Posted on July 12, 2015 - 20:32 (UTC)
Hcpookie
Random selections including negative numbers can be obtained via:
_Xrnd = round(random 200) -100;
This will yield numbers between -100 and 100.
  • Be careful using random numbers in multiplayer, each client will come up with a different result. See multiplayer tutorials for more general information about locality.
  • The number returned is unlikely to be a whole number.
To return a whole number use either round, ceil or floor together with random:
x = round (random 5) // will return 0, 1, 2, 3, 4 or 5. (non-uniform distribution, 0 and 5 are half as likely to be selected than any of the other numbers) x = floor (random 5) // will return 0, 1, 2, 3 or 4. (uniform distribution, all numbers have the same probability of being selected) x = ceil (random 5) // will return 0, 1, 2, 3, 4 or 5. (0 is very unlikely, but possible, as ceil 0 is 0)
Posted on July 22, 2018 - 12:58 (UTC+2)
Lou Montana
Repartition comparison
Formula 0 1 2 3 4 5 6 7 8 9
floor random 10; 10% 10% 10% 10% 10% 10% 10% 10% 10% 10%
floor random [0, 5, 10] 0% 2% 7% 17% 25% 25% 17% 7% 2% 0%
floor random [0, 10, 0] 0% 0% 1% 2% 5% 9% 14% 19% 24% 26%
floor random [0, 10, 5] 0% 0% 0% 1% 2% 5% 9% 16% 28% 38%
  1. Technically, it is a rescaled Bates distribution with n = 4. The distribution is split in two at its midpoint and scaled linearly such that its maximum lies at the specified midpoint.