
安装包与数据分类:

library(nnet) data("iris") set.seed(2) ind = sample(2,nrow(iris),replace = TRUE,prob = c(0.7,0.3)) trainset = iris[ind == 1,] testset = iris[ind == 2,]
使用nnet包训练神经网络:

iris.nn = nnet(Species ~ .,data = trainset,size = 2,rang = 0.1,decay = 5e-4,maxit = 200)
# weights: 19
initial value 114.539765
iter 10 value 52.100312
iter 20 value 50.231442
iter 30 value 49.526599
iter 40 value 49.402229
iter 50 value 44.680338
iter 60 value 5.254389
iter 70 value 2.836695
iter 80 value 2.744315
iter 90 value 2.687069
iter 100 value 2.621556
iter 110 value 2.589096
iter 120 value 2.410539
iter 130 value 2.096461
iter 140 value 1.938717
iter 150 value 1.857105
iter 160 value 1.825393
iter 170 value 1.817409
iter 180 value 1.815591
iter 190 value 1.815030
iter 200 value 1.814746
final value 1.814746
stoppedafter 200 iterations
调用summary()输出训练好的神经网络:

summary(iris.nn)
a 4-2-3 network with 19 weights
options were - softmax modelling decay=5e-04
b->h1 i1->h1 i2->h1 i3->h1 i4->h1
-20.60 0.31 -3.84 3.36 7.72
b->h2 i1->h2 i2->h2 i3->h2 i4->h2
-7.15 1.50 2.49 -4.14 5.59
b->o1 h1->o1 h2->o1
-7.28 -3.67 13.16
b->o2 h1->o2 h2->o2
15.90 -16.64 -19.40
b->o3 h1->o3 h2->o3
-8.62 20.31 6.24

iris.predict = predict(iris.nn,testset,type = "class")
nn.table = table(testset$Species,iris.predict)
nn.table
iris.predict
setosa versicolor virginica
setosa 17 0 0
versicolor 0 13 1
virginica 0 2 13confusionMatrix(nn.table)
Confusion Matrix and Statistics
iris.predict
setosa versicolor virginica
setosa 17 0 0
versicolor 0 13 1
virginica 0 2 13
Overall Statistics
Accuracy : 0.9348
95% CI : (0.821, 0.9863)
No Information Rate : 0.3696
P-Value [Acc > NIR] : 1.019e-15
Kappa : 0.9019
Mcnemar's Test P-Value : NA
Statistics by Class:
Class: setosa Class: versicolor Class: virginica
Sensitivity 1.0000 0.8667 0.9286
Specificity 1.0000 0.9677 0.9375
Pos Pred Value 1.0000 0.9286 0.8667
Neg Pred Value 1.0000 0.9375 0.9677
Prevalence 0.3696 0.3261 0.3043
Detection Rate 0.3696 0.2826 0.2826
Detection Prevalence 0.3696 0.3043 0.3261
Balanced Accuracy 1.0000 0.9172 0.9330
本文来自电脑杂谈,转载请注明本文网址:
http://www.pc-fly.com/a/jisuanjixue/article-133815-1.html
不然堂堂十四亿大国该何去何从