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56 lines
2.2 KiB
56 lines
2.2 KiB
4 weeks ago
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# weighted
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```js
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// usage
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chance.weighted(['a', 'b'], [100, 1])
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chance.weighted(['a', 'b', 'c', 'd'], [1, 2, 3, 4])
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```
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Provide an array of items, and another array of items specifying the relative weights and **Chance** will select one of those items, obeying the specified weight.
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For example, the following code:
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```js
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chance.weighted(['a', 'b'], [100, 1]);
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=> 'a'
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```
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Will generate `'a'` 100 times more often than `'b'` but still choose one or the other randomly.
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The weights are all relative, so if you have more than just two it will ensure that all items are generated relative to all of the weights.
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For example, the following code:
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```js
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chance.weighted(['a', 'b', 'c', 'd'], [1, 2, 3, 4]);
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=> 'c'
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```
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Will generate a letter from the array but will pick `'b'` twice as often as it picks `'a'` and will pick `'c'` three times as often as it picks `'a'` and will pick `'d'` four times as often as it will pick `'a'` and will pick `'d'` two times as often as it will pick `'b'`.
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The weights can be whole numbers as shown above or fractions.
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```js
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chance.weighted(['a', 'b', 'c', 'd'], [0.1, 0.2, 0.3, 0.4]);
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=> 'd'
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```
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There is no requirement that the weights sum to anything in particular, they are all compared relative to each other so all of the following are equivalent:
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```js
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chance.weighted(['a', 'b', 'c', 'd'], [1, 2, 3, 4]);
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chance.weighted(['a', 'b', 'c', 'd'], [0.1, 0.2, 0.3, 0.4]);
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chance.weighted(['a', 'b', 'c', 'd'], [100, 200, 300, 400]);
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chance.weighted(['a', 'b', 'c', 'd'], [17, 34, 51, 68]);
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chance.weighted(['a', 'b', 'c', 'd'], [0.17, 0.34, 0.51, 0.68]);
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```
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Recall JavaScript has first class functions so you could do something like the following:
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```js
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chance.weighted([chance.fbid, chance.twitter, chance.ip], [10, 5, 1])();
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=> 10000345166213
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```
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That will pick one of the **Chance** methods with the relative weights specified and then immediately invoke it, so it will return a random fbid twice as often as it will return a twitter handle (because 10/5 is 2) and an fbid 10 times more often than it will return a random ip address (because 10/1 is 10). It will return a random twitter handle 5 times more often than it will return an ip address (because 5/1 is 5).
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