38 lines
1.2 KiB
Text
38 lines
1.2 KiB
Text
// version 1.1.51
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fun polyRegression(x: IntArray, y: IntArray) {
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val n = x.size
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val r = 0 until n
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val xm = x.average()
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val ym = y.average()
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val x2m = r.map { it * it }.average()
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val x3m = r.map { it * it * it }.average()
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val x4m = r.map { it * it * it * it }.average()
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val xym = x.zip(y).map { it.first * it.second }.average()
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val x2ym = x.zip(y).map { it.first * it.first * it.second }.average()
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val sxx = x2m - xm * xm
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val sxy = xym - xm * ym
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val sxx2 = x3m - xm * x2m
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val sx2x2 = x4m - x2m * x2m
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val sx2y = x2ym - x2m * ym
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val b = (sxy * sx2x2 - sx2y * sxx2) / (sxx * sx2x2 - sxx2 * sxx2)
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val c = (sx2y * sxx - sxy * sxx2) / (sxx * sx2x2 - sxx2 * sxx2)
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val a = ym - b * xm - c * x2m
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fun abc(xx: Int) = a + b * xx + c * xx * xx
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println("y = $a + ${b}x + ${c}x^2\n")
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println(" Input Approximation")
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println(" x y y1")
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for (i in 0 until n) {
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System.out.printf("%2d %3d %5.1f\n", x[i], y[i], abc(x[i]))
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}
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}
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fun main(args: Array<String>) {
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val x = IntArray(11) { it }
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val y = intArrayOf(1, 6, 17, 34, 57, 86, 121, 162, 209, 262, 321)
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polyRegression(x, y)
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}
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