我一直在使用PyBrain创建神经网络，在使用传播训练后，它无法训练我的网络。无论我使用什么数据集，只要输出维度中有超过两个类别，所有的观测值都会被归到一个类别中。有人知道为什么会这样吗？下面是代码和一些输出。
训练的最后一个时期出现了0.09的错误，如下输出所示：
import scipy
import numpy
from pybrain.datasets import ClassificationDataSet
from pybrain.utilities import percentError
from pybrain.tools.shortcuts import buildNetwork
from pybrain.supervised.trainers import BackpropTrainer
from pybrain.structure.modules import SoftmaxLayer
from sklearn.metrics import precision_score,recall_score,confusion_matrix
def makeDataset(CSVfile,ClassFile):
#import the features to data, and their classes to dataClasses
data=numpy.genfromtxt(CSVfile,delimiter=",")
classes=numpy.genfromtxt(ClassFile,delimiter=",")
print("Building the dataset from CSV files")
#Initialize an empty Pybrain dataset, and populate it
alldata=ClassificationDataSet(len(data[0]),1,nb_classes=3)
for count in range(len((classes))):
alldata.addSample(data[count],[classes[count]])
return alldata
def makeNeuralNet(alldata,trainingPercent=.3,hiddenNeurons=5,trainingIterations=20):
#Divide the data set into training and non-training data
testData, trainData = alldata.splitWithProportion(trainingPercent)
testData._convertToOneOfMany( )
trainData._convertToOneOfMany( )
#Then build the network, and using backwards propogation to train it
network = buildNetwork( trainData.indim, hiddenNeurons, trainData.outdim, outclass=SoftmaxLayer )
trainer = BackpropTrainer( network, dataset=trainData, momentum=0.1, verbose=True, weightdecay=0.01)
for i in range(trainingIterations):
print("Training Epoch #"+str(i))
trainer.trainEpochs( 1 )
return [network,trainer]
def checkNeuralNet(trainer,alldata):
predictedVals=trainer.testOnClassData(alldata)
actualVals=list(alldata['target'])
## for row in alldata['target']:
## row=list(row)
## index=row.index(1)
## actualVals+=[index]
print("-----------------------------")
print("-----------------------------")
print("The precision is "+str(precision_score(actualVals,predictedVals)))
print("The recall is "+str(recall_score(actualVals,predictedVals)))
print("The confusion matrix is as shown below:")
print(confusion_matrix(actualVals,predictedVals))
CSVfile="/home/ubuntu/test.csv"
ClassFile="/home/ubuntu/test_Classes.csv"
#Build our dataset
alldata=makeDataset(CSVfile,ClassFile)
#Build and train the network
net=makeNeuralNet(alldata,trainingPercent=.7,hiddenNeurons=20,trainingIterations=20)
network=net[0]
trainer=net[1]
#Check it's strength
checkNeuralNet(trainer,alldata)
训练的最后一个时期出现了0.09的错误，如下输出所示：
Training Epoch #19
Total error: 0.0968444196605
然而，当我要打印混淆矩阵、精确度和召回率时，我得到了以下结果以及这个奇怪的错误：
UserWarning: The sum of true positives and false positives are equal to zero for some labels. Precision is ill defined for those labels [1 2]. The precision and recall are equal to zero for some labels. fbeta_score is ill defined for those labels [1 2].
average=average)
The precision is 0.316635552252
UserWarning: The sum of true positives and false positives are equal to zero for some labels. Precision is ill defined for those labels [1 2]. The precision and recall are equal to zero for some labels. fbeta_score is ill defined for those labels [1 2].
average=average)
The recall is 0.562703787309
The confusion matrix is as shown below:
[[4487 0 0]
[ 987 0 0]
[2500 0 0]]