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使用Pytorch框架实现简单的数据分类(7)


(1)代码中使用的函数简要介绍

torch.normal  #张量里面的随机数是从相互独立的正态分布中随机生成的。
torch.cat #将两个张量(tensor)拼接在一起

(2)代码

import torch
from torch.autograd import Variable
import torch.nn.functional as F
import matplotlib.pyplot as plt

# torch.manual_seed(1) # reproducible

#制造训练数据
n_data = torch.ones(100, 2)
x0 = torch.normal(2*n_data, 1) # class0 x data (tensor), shape=(100, 2)
y0 = torch.zeros(100) # class0 y data (tensor), shape=(100, 1)
x1 = torch.normal(-2*n_data, 1) # class1 x data (tensor), shape=(100, 2)
y1 = torch.ones(100) # class1 y data (tensor), shape=(100, 1)
x = torch.cat((x0, x1), 0).type(torch.FloatTensor) # shape (200, 2) FloatTensor = 32-bit floating
y = torch.cat((y0, y1), ).type(torch.LongTensor) # shape (200,) LongTensor = 64-bit integer

'''
# The code below is deprecated in Pytorch 0.4. Now, autograd directly supports tensors
x, y = Variable(x), Variable(y)

plt.scatter(x.data.numpy()[:, 0], x.data.numpy()[:, 1], c=y.data.numpy(), s=100, lw=0, cmap='RdYlGn')
plt.show()
'''
class Net(torch.nn.Module):
def __init__(self, n_feature, n_hidden, n_output):
super(Net, self).__init__()
self.hidden = torch.nn.Linear(n_feature, n_hidden) # hidden layer
self.out = torch.nn.Linear(n_hidden, n_output) # output layer

def forward(self, x):
x = F.relu(self.hidden(x)) # activation function for hidden layer
x = self.out(x)
return x

net = Net(n_feature=2, n_hidden=10, n_output=2) # define the network
print(net) # net architecture

optimizer = torch.optim.SGD(net.parameters(), lr=0.02)
loss_func = torch.nn.CrossEntropyLoss() # the target label is NOT an one-hotted

plt.ion() # something about plotting

for t in range(1000):
out = net(x) # input x and predict based on x
loss = loss_func(out, y) # must be (1. nn output, 2. target), the target label is NOT one-hotted

optimizer.zero_grad() # clear gradients for next train
loss.backward() # backpropagation, compute gradients
optimizer.step() # apply gradients

if t % 2 == 0:
# plot and show learning process
plt.cla()
prediction = torch.max(out, 1)[1]
pred_y = prediction.data.numpy()
target_y = y.data.numpy()
plt.scatter(x.data.numpy()[:, 0], x.data.numpy()[:, 1], c=pred_y, s=100, lw=0, cmap='RdYlGn')
accuracy = float((pred_y == target_y).astype(int).sum()) / float(target_y.size)
plt.text(1.5, -4, 'Accuracy=%.2f' % accuracy, fontdict={'size': 20, 'color': 'red'})
plt.pause(1)

plt.ioff()
plt.show()

(3)代码运行结果

使用Pytorch框架实现简单的数据分类(7)_数据分类

注:本文中代码主要参考链接:​​https://github.com/MorvanZhou​​

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