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June 29, 2020 18:30
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Get `n` random numbers between 2 given numbers having average `x`
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function getRandom(min, max) { | |
return Math.random() * (max - min) + min; | |
} | |
function getArr(size, avg, min, max) { | |
let arr = []; | |
let tmax = max; | |
let tmin = min; | |
while (arr.length < size) { | |
const variable1 = +getRandom(min, tmax).toFixed(1); | |
let variable2 = +(avg * 2 - variable1).toFixed(1); | |
if (variable2 < min) { | |
tmax = max - (min - variable2); | |
variable2 = min; | |
} else if (variable2 > max) { | |
tmin = min + (variable2 - max); | |
variable2 = max; | |
} else { | |
tmax = max; | |
tmin = min; | |
} | |
arr = arr.concat([variable1, variable2]); | |
} | |
let sumErr = arr.reduce((a, b) => a + b, 0) - avg * size; | |
if (sumErr > 0) { | |
arr = arr.map((x) => { | |
if (x > min && sumErr > 0.001) { | |
let maxReduce = x - min; | |
if (maxReduce > sumErr) { | |
const toReturn = +(x - sumErr).toFixed(1); | |
sumErr = 0; | |
return toReturn; | |
} else { | |
sumErr -= maxReduce; | |
return min; | |
} | |
} | |
return x; | |
}); | |
} else { | |
arr = arr.map((x) => { | |
if (x < max && sumErr < -0.001) { | |
let maxAdd = max - x; | |
if (maxAdd > Math.abs(sumErr)) { | |
const toReturn = +(x + Math.abs(sumErr)).toFixed(1); | |
sumErr = 0; | |
return toReturn; | |
} else { | |
sumErr += maxAdd; | |
return max; | |
} | |
} | |
return x; | |
}); | |
} | |
return arr.sort(() => Math.random() - 0.5); | |
} | |
getArr(10, 2.01, 0.5, 2.5); // [0.5, 3.8, 2.4, 3.4, 0.5, 3.8, 0.6, 0.5, 0.7, 3.9] |
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