How many to solve to improve percentile using ramda.js

QantilevsMedian.js

// sort array ascending
const asc = arr => arr.sort((a, b) => a - b);

// sample standard deviation
const std = (arr) => {
  const mu = mean(arr)
  const diffArr = arr.map(a => (a - mu) ** 2)
  return Math.sqrt(sum(diffArr) / (arr.length - 1))
}

const quantile = (arr, q) => {
  const sorted = asc(arr)
  const pos = (sorted.length - 1) * q
  const base = Math.floor(pos)
  const rest = pos - base
  if (sorted[base + 1] !== undefined) {
    return sorted[base] + rest * (sorted[base + 1] - sorted[base])
  } else {
    return sorted[base]
  }
}

const median2 = arr => quantile(arr, .50) 
// same as R.median

median2(arr) === median(arr)

const arr = [1,2,3,4,5,6,7,8,9,10]

const percentile = (arr, val) =>
  (100 *
    arr.reduce(
      (acc, v) => acc + (v < val ? 1 : 0) + (v === val ? 0.5 : 0),
      0
    )) /
  arr.length

percentile(arr, 6) // => 55
quantile(arr, .55) // 5.95
quantile(arr, .70) - quantile(arr, .55)
// need increase of 1.35 to get to 70% percentile
percentile(arr, 6 + 1.3499999999999996) // 70