bc518174
 王天杨
提交两个项目文件
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export class MonotonicInterpolant {
private xs: any
private ys: any
private c1s: any
private c2s: any
private c3s: any
public constructor(xs: number[], ys: number[]) {
const { length } = xs
// Rearrange xs and ys so that xs is sorted
const indexes = []
for (let i = 0; i < length; i++) {
indexes.push(i)
}
indexes.sort((a, b) => ((xs[a] as number) < (xs[b] as number) ? -1 : 1))
// Get consecutive differences and slopes
const dys = []
const dxs = []
const ms = []
let dx
let dy
for (let i = 0; i < length - 1; i++) {
dx = (xs[i + 1] as number) - (xs[i] as number)
dy = (ys[i + 1] as number) - (ys[i] as number)
dxs.push(dx)
dys.push(dy)
ms.push(dy / dx)
}
// Get degree-1 coefficients
const c1s = [ms[0]]
for (let i = 0; i < dxs.length - 1; i++) {
const m2 = ms[i] as number
const mNext = ms[i + 1] as number
if (m2 * mNext <= 0) {
c1s.push(0)
} else {
dx = dxs[i] as number
const dxNext = dxs[i + 1] as number
const common = dx + dxNext
c1s.push(
(3 * common) / ((common + dxNext) / m2 + (common + dx) / mNext),
)
}
}
c1s.push(ms[ms.length - 1])
// Get degree-2 and degree-3 coefficients
const c2s = []
const c3s = []
let m
for (let i = 0; i < c1s.length - 1; i++) {
m = ms[i] as number
const c1 = c1s[i] as number
const invDx = 1 / (dxs[i] as number)
const common = c1 + (c1s[i + 1] as number) - m - m
c2s.push((m - c1 - common) * invDx)
c3s.push(common * invDx * invDx)
}
this.xs = xs
this.ys = ys
this.c1s = c1s
this.c2s = c2s
this.c3s = c3s
}
public interpolate(x: number): number {
const { xs, ys, c1s, c2s, c3s } = this
// The rightmost point in the dataset should give an exact result
let i = xs.length - 1
if (x === xs[i]) {
return ys[i]
}
// Search for the interval x is in, returning the corresponding y if x is one of the original xs
let low = 0
let high = c3s.length - 1
let mid
while (low <= high) {
mid = Math.floor(0.5 * (low + high))
const xHere = xs[mid]
if (xHere < x) {
low = mid + 1
} else if (xHere > x) {
high = mid - 1
} else {
return ys[mid]
}
}
i = Math.max(0, high)
// Interpolate
const diff = x - xs[i]
const diffSq = diff * diff
return ys[i] + c1s[i] * diff + c2s[i] * diffSq + c3s[i] * diff * diffSq
}
}
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