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quick and dirty javascript "lib" to prepare for a statistics exam
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'use strict'; | |
var _fstore = []; | |
function factorial (n) { | |
if (n == 0 || n == 1) { | |
return 1; | |
} | |
if (_fstore[n] > 0) { | |
return _fstore[n]; | |
} | |
return _fstore[n] = factorial(n - 1) * n; | |
} | |
module.exports = { | |
binomial: (n, x, prob) => { | |
if ((n >= x) && (prob <= 1) && (prob >= 0) && Number.isInteger(n) && Number.isInteger(x) && ( x >= 0)) { | |
return (factorial(n) / (factorial(n - x) * factorial(x))) * Math.pow(prob, x) * Math.pow(1 - prob, n - x); | |
} else { | |
console.log("expected: n, x, p"); | |
} | |
}, | |
factorial: factorial, | |
distinguishable_sequence: obj => { | |
if (obj !== null && typeof obj === 'object') { | |
let values = Object.values(obj); | |
if (values.every(Number.isInteger)) { | |
let n = values.reduce((a, b) => a + b); | |
let denum = values.reduce((a, b) => "" + a + "! " + b) + "!"; | |
console.log(n + "!"); | |
console.log("-".repeat(denum.length)); | |
console.log(denum); | |
return factorial(n) / (values.reduce((a, b) => a * factorial(b))); | |
} | |
} else { | |
console.log("expected object with string/integer pairs"); | |
} | |
} | |
}; |
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