[英]Model selection in R, all models giving the same AIC and BIC
所以这是我的数据的头,
thickness grains resistivity
1 25.1 14.9 0.0270
2 368.4 58.1 0.0267
3 540.4 77.3 0.0160
4 712.1 95.6 0.0105
5 883.7 113.0 0.0090
6 1055.7 130.0 0.0247
我想找到三种不同型号的AIC和BIC,包括厚度和颗粒。
AIC(lm(formula = resistivity ~ (1/thickness), data=z)) #142.194
BIC(lm(formula = resistivity ~ (1/thickness), data=z)) #142.9898
AIC(lm(formula = resistivity ~ (1/grains), data=z)) #142.194
BIC(lm(formula = resistivity ~ (1/grains), data=z)) #142.9898
AIC(lm(formula = resistivity ~ (1/thickness) + (1/grains), data=z)) #142.194
BIC(lm(formula = resistivity ~ (1/thickness) + (1/grains), data=z)) #142.9898
我对每个旁边的输出进行了评论,为什么它们都一样?
您获得相同的AIC和BIC,因为模型都是相同的。 你只是得到一个常数,即电阻率的平均值。
lm(formula = resistivity ~ (1/thickness), data = z)
Coefficients:
(Intercept)
0.01898
问题是如果你想在公式中进行像1 /厚度这样的计算,你必须在公式中通过将计算括在I()
。 这在help(formula)
描述。 你想要的是什么
lm(formula = resistivity ~ I(1/thickness), data=z)
lm(formula = resistivity ~ I(1/grains), data=z)
lm(formula = resistivity ~ I(1/thickness) + I(1/grains), data=z)
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