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我对拟合的残差平方和有疑问。残差的平方和太高，说明拟合不是很好。但是，从视觉上看，拥有如此高的剩余价值看起来不错……谁能帮我知道发生了什么？

我的数据：

x=c(0.017359, 0.019206, 0.020619, 0.021022, 0.021793, 0.022366, 0.025691, 0.025780, 0.026355, 0.028858, 0.029766, 0.029967, 0.030241, 0.032216, 0.033657,
 0.036250, 0.039145, 0.040682, 0.042334, 0.043747, 0.044165, 0.044630, 0.046045, 0.048138, 0.050813, 0.050955, 0.051910, 0.053042, 0.054853, 0.056886,
0.058651, 0.059472, 0.063770,0.064567, 0.067415, 0.067802, 0.068995, 0.070742,0.073486, 0.074085 ,0.074452, 0.075224, 0.075853, 0.076192, 0.077002,
 0.078273, 0.079376, 0.083269, 0.085902, 0.087619, 0.089867, 0.092606, 0.095944, 0.096327, 0.097019, 0.098444, 0.098868, 0.098874, 0.102027, 0.103296,
 0.107682, 0.108392, 0.108719, 0.109184, 0.109623, 0.118844, 0.124023, 0.124244, 0.129600, 0.130892, 0.136721, 0.137456, 0.147343, 0.149027, 0.152818,
0.155706,0.157650, 0.161060, 0.162594, 0.162950, 0.165031, 0.165408, 0.166680, 0.167727, 0.172882, 0.173264, 0.174552,0.176073, 0.185649, 0.194492,
 0.196429, 0.200050, 0.208890, 0.209826, 0.213685, 0.219189, 0.221417, 0.222662, 0.230860, 0.234654, 0.235211, 0.241819, 0.247527, 0.251528, 0.253664,
 0.256740, 0.261723, 0.274585, 0.278340, 0.281521, 0.282332, 0.286166, 0.288103, 0.292959, 0.295201, 0.309456, 0.312158, 0.314132, 0.319906, 0.319924,
 0.322073, 0.325427, 0.328132, 0.333029, 0.334915, 0.342098, 0.345899, 0.345936, 0.350355, 0.355015, 0.355123, 0.356335, 0.364257, 0.371180, 0.375171,
0.377743, 0.383944, 0.388606, 0.390111, 0.395080, 0.398209, 0.409784, 0.410324, 0.424782 )


y= c(34843.40, 30362.66, 27991.80 ,28511.38, 28004.74, 27987.13, 22272.41, 23171.71, 23180.03, 20173.79, 19751.84, 20266.26, 20666.72, 18884.42, 17920.78, 15980.99, 14161.08, 13534.40, 12889.18, 12436.11,
12560.56, 12651.65, 12216.11, 11479.18, 10573.22, 10783.99, 10650.71, 10449.87, 10003.68,  9517.94,  9157.04,  9104.01,  8090.20,  8059.60,  7547.20,  7613.51,  7499.47,  7273.46,  6870.20,  6887.01,
6945.55,  6927.43,  6934.73,  6993.73,  6965.39,  6855.37,  6777.16,  6259.28,  5976.27,  5835.58,  5633.88,  5387.19,  5094.94,  5129.89,  5131.42,  5056.08,  5084.47,  5155.40,  4909.01,  4854.71,
4527.62,  4528.10,  4560.14,  4580.10,  4601.70,  3964.90,  3686.20,  3718.46,  3459.13,  3432.05,  3183.09,  3186.18,  2805.15,  2773.65,  2667.73,  2598.55,  2563.02,  2482.63,  2462.49,  2478.10,
2441.70,  2456.16,  2444.00,  2438.47,  2318.64,  2331.75,  2320.43,  2303.10,  2091.95,  1924.55, 1904.91,  1854.07,  1716.52,  1717.12,  1671.00,  1602.70,  1584.89,  1581.34,  1484.16,  1449.26,
1455.06,  1388.60,  1336.71,  1305.60,  1294.58,  1274.36,  1236.51,  1132.67,  1111.35,  1095.21,  1097.71,  1077.05,  1071.04,  1043.99,  1036.22,   950.26,   941.06,   936.37,   909.72,   916.45,
911.01, 898.94,   890.68,   870.99,   867.45,   837.39,   824.93,   830.61,   815.49,   799.77,   804.84,   804.88,   775.53,   751.95,   741.01,   735.86,   717.03,   704.57,   703.74,   690.63,
684.24,   650.30,   652.74,   612.95 )

然后使用 nlsLM 函数（minpack.lm 包）进行拟合：

library(magicaxis)
library(minpack.lm)

sig.backg=3*10^(-3) 

mod <- nlsLM(y ~ a *( 1 + (x/b)^2 )^c+sig.backg,
             start = c(a = 0, b = 1, c = 0),
             trace = TRUE)

## plot data
magplot(x, y, main = "data", log = "xy", pch=16)
## plot fitted values
lines(x, fitted(mod), col = 2, lwd = 4 )

情节：点和拟合

这个值是残差：

> print(mod)
Nonlinear regression model
  model: y ~ a * (1 + (x/b)^2)^c + sig.backg
   data: parent.frame()
         a          b          c 
68504.2013     0.0122    -0.6324 
 residual sum-of-squares: 12641435

Number of iterations to convergence: 34 
Achieved convergence tolerance: 0.0000000149

平方和残差太高：12641435 ...

是这样还是调整有问题？这是坏的？

4

2 回答 2

2

这是有道理的，因为您的响应变量的平方平均值是 38110960。如果您喜欢使用较小的数字，您可以缩放您的数据。

于 2016-01-27T14:59:16.837 回答
1

如果不知道总平方和（从中可以计算 R^2），残差平方和没有多大意义。如果您的数据具有较大的值或添加更多数据点，无论您的拟合程度如何，它的价值都会增加。此外，您可能希望查看残差与拟合数据的图，有一个清晰的模式应该由您的模型解释，以确保您的错误是正态分布的。

于 2016-01-27T15:04:57.100 回答