我正在尝试使用8个类来适应卷积神经网络(在Keras中)的Python代码来处理2个类 . 我的问题是我收到以下错误消息:
ValueError:检查目标时出错:预期activation_6具有形状(None,2)但是具有形状的数组(5760,1) .
我的模型如下(没有缩进问题):
class MiniVGGNet:
@staticmethod
def build(width, height, depth, classes):
# initialize the model along with the input shape to be
# "channels last" and the channels dimension itself
model = Sequential()
inputShape = (height, width, depth)
chanDim = -1
# if we are using "channels first", update the input shape
# and channels dimension
if K.image_data_format() == "channels_first":
inputShape = (depth, height, width)
chanDim = 1
# first CONV => RELU => CONV => RELU => POOL layer set
model.add(Conv2D(32, (3, 3), padding="same",
input_shape=inputShape))
model.add(Activation("relu"))
model.add(BatchNormalization(axis=chanDim))
model.add(Conv2D(32, (3, 3), padding="same"))
model.add(Activation("relu"))
model.add(BatchNormalization(axis=chanDim))
model.add(MaxPooling2D(pool_size=(2, 2)))
model.add(Dropout(0.25))
# second CONV => RELU => CONV => RELU => POOL layer set
model.add(Conv2D(64, (3, 3), padding="same"))
model.add(Activation("relu"))
model.add(BatchNormalization(axis=chanDim))
model.add(Conv2D(64, (3, 3), padding="same"))
model.add(Activation("relu"))
model.add(BatchNormalization(axis=chanDim))
model.add(MaxPooling2D(pool_size=(2, 2)))
model.add(Dropout(0.25))
# first (and only) set of FC => RELU layers
model.add(Flatten())
model.add(Dense(512))
model.add(Activation("relu"))
model.add(BatchNormalization())
model.add(Dropout(0.5))
# softmax classifier
model.add(Dense(classes))
model.add(Activation("softmax"))
# return the constructed network architecture
return model
其中classes = 2,inputShape =(32,32,3) .
我知道我的错误与我的类/使用binary_crossentropy有关,并且发生在下面的model.fit行中,但是无法弄清楚它为什么有问题,或者如何修复它 .
通过将上面的model.add(Dense(classes))更改为model.add(Dense(classes-1)),我可以获得要训练的模型,但是我的标签大小和target_names不匹配,我只有一个类别,一切被归类为 .
# import the necessary packages
from sklearn.preprocessing import LabelBinarizer
from sklearn.model_selection import train_test_split
from sklearn.metrics import classification_report
from pyimagesearch.nn.conv import MiniVGGNet
from pyimagesearch.preprocessing import ImageToArrayPreprocessor
from pyimagesearch.preprocessing import SimplePreprocessor
from pyimagesearch.datasets import SimpleDatasetLoader
from keras.optimizers import SGD
#from keras.datasets import cifar10
from imutils import paths
import matplotlib.pyplot as plt
import numpy as np
import argparse
# construct the argument parse and parse the arguments
ap = argparse.ArgumentParser()
ap.add_argument("-d", "--dataset", required=True,
help="path to input dataset")
ap.add_argument("-o", "--output", required=True,
help="path to the output loss/accuracy plot")
args = vars(ap.parse_args())
# grab the list of images that we'll be describing
print("[INFO] loading images...")
imagePaths = list(paths.list_images(args["dataset"]))
# initialize the image preprocessors
sp = SimplePreprocessor(32, 32)
iap = ImageToArrayPreprocessor()
# load the dataset from disk then scale the raw pixel intensities
# to the range [0, 1]
sdl = SimpleDatasetLoader(preprocessors=[sp, iap])
(data, labels) = sdl.load(imagePaths, verbose=500)
data = data.astype("float") / 255.0
# partition the data into training and testing splits using 75% of
# the data for training and the remaining 25% for testing
(trainX, testX, trainY, testY) = train_test_split(data, labels,
test_size=0.25, random_state=42)
# convert the labels from integers to vectors
trainY = LabelBinarizer().fit_transform(trainY)
testY = LabelBinarizer().fit_transform(testY)
# initialize the label names for the items dataset
labelNames = ["mint", "used"]
# initialize the optimizer and model
print("[INFO] compiling model...")
opt = SGD(lr=0.01, decay=0.01 / 10, momentum=0.9, nesterov=True)
model = MiniVGGNet.build(width=32, height=32, depth=3, classes=2)
model.compile(loss="binary_crossentropy", optimizer=opt,
metrics=["accuracy"])
# train the network
print("[INFO] training network...")
H = model.fit(trainX, trainY, validation_data=(testX, testY),
batch_size=64, epochs=10, verbose=1)
print ("Made it past training")
# evaluate the network
print("[INFO] evaluating network...")
predictions = model.predict(testX, batch_size=64)
print(classification_report(testY.argmax(axis=1),
predictions.argmax(axis=1), target_names=labelNames))
# plot the training loss and accuracy
plt.style.use("ggplot")
plt.figure()
plt.plot(np.arange(0, 10), H.history["loss"], label="train_loss")
plt.plot(np.arange(0, 10), H.history["val_loss"], label="val_loss")
plt.plot(np.arange(0, 10), H.history["acc"], label="train_acc")
plt.plot(np.arange(0, 10), H.history["val_acc"], label="val_acc")
plt.title("Training Loss and Accuracy on items dataset")
plt.xlabel("Epoch #")
plt.ylabel("Loss/Accuracy")
plt.legend()
plt.savefig(args["output"])
我已经看过这些问题,但无法根据回答来解决这个问题 .
我会非常感谢任何建议或帮助,因为我花了最近几天的时间 .
2 回答
我认为问题在于使用
LabelBinarizer
.从这个例子:
我认为你的转换输出具有相同的格式,i . 即单个
1
或0
编码"is new"或"is used" .如果你的问题只是要求在这两个类之间进行分类,那么这种格式是可取的,因为它包含所有信息并且使用的空间比替代方案少,i . 即
[1,0], [0,1], [0,1], [1,0]
.因此,使用
classes = 1
是正确的,输出应该是一个浮点数,表示网络对第一类中的样本的置信度 . 由于这些值必须总和为1,因此通过从1减去可以很容易地推断出它在第二类中的概率 .您需要将
softmax
替换为任何其他激活,因为单个值上的softmax始终返回1.我不完全确定具有单值结果的binary_crossentropy
的行为,并且您可能想要尝试mean_squared_error
作为丢失 .如果您希望扩展模型以涵盖两个以上的类,则需要将目标矢量转换为One-hot编码 . 我相信来自
LabelBinarizer
的inverse_transform
会做到这一点,尽管那似乎是一种相当迂回的方式来实现目标 . 我看到sklearn也有OneHotEncoder
,这可能是更合适的替代品 .注意:您可以更轻松地为任何图层指定激活功能,例如:
这可能有助于将代码保持在可管理的大小 .
Matt的评论是完全正确的,因为问题在于使用LabelBinarizer,这个提示让我得到了一个解决方案,它不需要我放弃使用softmax,或者更改最后一层以使class = 1.对于后代和其他人来说,这里是我改变的代码部分以及我如何能够避免LabelBinarizer: