Polynomial regression: Difference between revisions

=={{header|Nim}}==

{{trans|Kotlin}}

<lang Nim>import lenientops, sequtils, stats, strformat

proc polyRegression(x, y: openArray[int]) =

let xm = mean(x)

let ym = mean(y)

let x2m = mean(x.mapIt(it * it))

let x3m = mean(x.mapIt(it * it * it))

let x4m = mean(x.mapIt(it * it * it * it))

let xym = mean(zip(x, y).mapIt(it[0] * it[1]))

let x2ym = mean(zip(x, y).mapIt(it[0] * it[0] * it[1]))

let sxx = x2m - xm * xm

let sxy = xym - xm * ym

let sxx2 = x3m - xm * x2m

let sx2x2 = x4m - x2m * x2m

let sx2y = x2ym - x2m * ym

let b = (sxy * sx2x2 - sx2y * sxx2) / (sxx * sx2x2 - sxx2 * sxx2)

let c = (sx2y * sxx - sxy * sxx2) / (sxx * sx2x2 - sxx2 * sxx2)

let a = ym - b * xm - c * x2m

func abc(x: int): float = a + b * x + c * x * x

echo &"y = {a} + {b}x + {c}x²\n"

echo " Input Approximation"

echo " x y y1"

for (xi, yi) in zip(x, y):

echo &"{xi:2} {yi:3} {abc(xi):5}"

let x = toSeq(0..10)

let y = [1, 6, 17, 34, 57, 86, 121, 162, 209, 262, 321]

polyRegression(x, y)</lang>

{{out}}

<pre>y = 1.0 + 2.0x + 3.0x²

Input Approximation

x y y1

0 1 1

1 6 6

2 17 17

3 34 34

4 57 57

5 86 86

6 121 121

7 162 162

8 209 209

9 262 262

10 321 321</pre>