#[
线性拟合的例子
参考 https://zhuanlan.zhihu.com/p/80969579
使用 https://nim-lang.org/ 实现
]#

import math
import lenientops
import strformat

proc mean(x: seq[float|float32|int]): float32 =
    return x.sum/x.len

proc `*`[A: float|float32|int, B: float|float32|int](x: seq[A], y: seq[B]): seq[float32] =
    for i in 0 ..< len(x):
        result.add float32(x[i] * y[i])
    return result

proc `-`[A: float|float32|int, B: float|float32|int](x: seq[A], y: seq[B]): seq[float32] =
    for i in 0 ..< len(x):
        result.add float32(x[i] - y[i])
    return result

proc `*`(n:float|int, y: seq[float|float32|int]): seq[float32] =
    for i in 0 ..< len(y):
        result.add float32(n * y[i])
    return result

proc `-`(x: seq[float|float32|int], n:float|float32|int): seq[float32] =
    for i in 0 ..< len(x):
        result.add float32(x[i] - n)
    return result

var
    x = @[427, 459, 611, 593, 588]
    y = @[-49.18, -22.21, 55.96, 117.37, 119.74]

var
    mean_x = mean(x)
    w = (y*(x - mean_x)).sum()/((x*x).sum()-x.sum()*x.sum()/len(x))
    b = (y-w*x).sum()/len(x)

echo fmt"线性拟合得到的方程为y = {w:.2f}*x + {b:.2f}"
echo fmt"煤价为{-b/w:.2f}时,净利润为0"

【 在 chh811 (chh) 的大作中提到: 】
: 类别    2015年    2016年    2017年    2018年    2019年
: 煤价    427    459    611    593    588  
: 净利润    -49.18    -22.21    55.96    117.37    119.74  
: ...................
--
FROM 117.140.170.*