Math.Random high chance to low numbers

[zxmatzx]

Hi folks, i'm needing help with a function. I need a function that receive 2 integers numbers and return a random number between them with bigger chance to get small numbers instead big numbers. Could work with percents interval?

I've found on internet some ideas, like random weighted numbers generator, i had some troubles trying adapt the code to my necessitys.
I would like understand how this code work, i'll keep trying, but would be nice recive anothers approach to do that.

Thanks.

 

[StreamSide]

Just did a quick search on stackoverflow and found this:
Random number generator with higher probabilities of giving low values? (https://stackoverflow.com/questions/4420502/random-number-generator-with-higher-probabilities-of-giving-low-values/4421297#4421297)
You can actually create a function with it.

function getRandomNumber(max, min, probabilityPower)
    return math.floor(min + (max + 1 - min) * (math.random() ^ probabilityPower))
end

quoting the author message:

If probabilityPower is above 1, lower values will be more common than higher values. If it's between 0 to 1, higher values will be more common than lower values. If it's 1, the results will be in a general randomness.

Examples (all with 1 million iterations, min = 1, max = 20 ):

Spoiler: probabilityPower = 4

1: 471570 (47.157%)
2: 90114 (9.0114%)
3: 60333 (6.0333%)
4: 46574 (4.6574%)
5: 38905 (3.8905%)
6: 32379 (3.2379%)
7: 28309 (2.8309%)
8: 27906 (2.7906%)
9: 22389 (2.2389%)
10: 21524 (2.1524%)
11: 19444 (1.9444%)
12: 19688 (1.9688%)
13: 18398 (1.8398%)
14: 16870 (1.687%)
15: 15517 (1.5517%)
16: 15871 (1.5871%)
17: 14550 (1.455%)
18: 14635 (1.4635%)
19: 13399 (1.3399%)
20: 11625 (1.1625%)

Spoiler: probabilityPower = 1

1: 51534 (5.1534%)
2: 49239 (4.9239%)
3: 50955 (5.0955%)
4: 47992 (4.7992%)
5: 48971 (4.8971%)
6: 50456 (5.0456%)
7: 49282 (4.9282%)
8: 51344 (5.1344%)
9: 50841 (5.0841%)
10: 48548 (4.8548%)
11: 49294 (4.9294%)
12: 51795 (5.1795%)
13: 50583 (5.0583%)
14: 51020 (5.102%)
15: 51060 (5.106%)
16: 48632 (4.8632%)
17: 48568 (4.8568%)
18: 50039 (5.0039%)
19: 49863 (4.9863%)
20: 49984 (4.9984%)

Spoiler: probabilityPower = 0.5

1: 3899 (0.3899%)
2: 5818 (0.5818%)
3: 12808 (1.2808%)
4: 17880 (1.788%)
5: 23109 (2.3109%)
6: 26469 (2.6469%)
7: 33435 (3.3435%)
8: 35243 (3.5243%)
9: 42276 (4.2276%)
10: 47235 (4.7235%)
11: 52907 (5.2907%)
12: 58107 (5.8107%)
13: 63719 (6.3719%)
14: 66266 (6.6266%)
15: 72708 (7.2708%)
16: 79257 (7.9257%)
17: 81830 (8.183%)
18: 87243 (8.7243%)
19: 90958 (9.0958%)
20: 98833 (9.8833%)

 

[zxmatzx]

Just did a quick search on stackoverflow and found this:
Random number generator with higher probabilities of giving low values? (https://stackoverflow.com/questions/4420502/random-number-generator-with-higher-probabilities-of-giving-low-values/4421297#4421297)
You can actually create a function with it.

function getRandomNumber(max, min, probabilityPower)
    return math.floor(min + (max + 1 - min) * (math.random() ^ probabilityPower))
end

quoting the author message:

Thanks for help, i found this way when i was searching too. Already looked to the formula with a math perspective too. Just seeking others ways to do the same thing xD
I send the problem to a math teacher friend, he told to do:
"Do a algorithm to get 100 numbers to
represent 30% first numbers, 50 numbers to 50% and 10 numbers to 20% last numbers, then get a random number in all these 160 numbers and u will have more chance to get a lower-middle number"
I don't know how method i will use for my code, just looking and geting info.
Thanks a lot for help.

PS: Your answer can be the best answer, but how i said, im looking many ways to do the same thing. I have to close thread now?