在张量流中微调神经网络

Question

I've been working on this neural network with the intent to predict TBA (time based availability) of simulated windmill parks based on certain attributes. The neural network runs just fine, and gives me some predictions, however I'm not quite satisfied with the results. It fails to notice some very obvious correlations that I can clearly see by myself. Here is my current code:

`# Import
import tensorflow as tf
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt

from sklearn.preprocessing import MinMaxScaler

maxi = 0.96 
mini = 0.7 


# Make data a np.array
data = pd.read_csv('datafile_ML_no_avg.csv')
data = data.values

# Shuffle the data
shuffle_indices = np.random.permutation(np.arange(len(data)))
data = data[shuffle_indices]

# Training and test data
data_train = data[0:int(len(data)*0.8),:]
data_test = data[int(len(data)*0.8):int(len(data)),:]

# Scale data
scaler = MinMaxScaler(feature_range=(mini, maxi))
scaler.fit(data_train)
data_train = scaler.transform(data_train)
data_test = scaler.transform(data_test)


# Build X and y
X_train = data_train[:, 0:5]
y_train = data_train[:, 6:7]
X_test = data_test[:, 0:5]
y_test = data_test[:, 6:7]

# Number of stocks in training data
n_args = X_train.shape[1]
multi = int(8)
# Neurons
n_neurons_1 = 8*multi
n_neurons_2 = 4*multi
n_neurons_3 = 2*multi
n_neurons_4 = 1*multi

# Session
net = tf.InteractiveSession()

# Placeholder
X = tf.placeholder(dtype=tf.float32, shape=[None, n_args])
Y = tf.placeholder(dtype=tf.float32, shape=[None,1])

# Initialize1s
sigma = 1
weight_initializer = tf.variance_scaling_initializer(mode="fan_avg",                             
distribution="uniform", scale=sigma)
bias_initializer = tf.zeros_initializer()

# Hidden weights
W_hidden_1 = tf.Variable(weight_initializer([n_args, n_neurons_1]))
bias_hidden_1 = tf.Variable(bias_initializer([n_neurons_1]))
W_hidden_2 = tf.Variable(weight_initializer([n_neurons_1, n_neurons_2]))
bias_hidden_2 = tf.Variable(bias_initializer([n_neurons_2]))
W_hidden_3 = tf.Variable(weight_initializer([n_neurons_2, n_neurons_3]))
bias_hidden_3 = tf.Variable(bias_initializer([n_neurons_3]))
W_hidden_4 = tf.Variable(weight_initializer([n_neurons_3, n_neurons_4]))
bias_hidden_4 = tf.Variable(bias_initializer([n_neurons_4]))

# Output weights
W_out = tf.Variable(weight_initializer([n_neurons_4, 1]))
bias_out = tf.Variable(bias_initializer([1]))

# Hidden layer
hidden_1 = tf.nn.relu(tf.add(tf.matmul(X, W_hidden_1), bias_hidden_1))
hidden_2 = tf.nn.relu(tf.add(tf.matmul(hidden_1, W_hidden_2),         
bias_hidden_2))
hidden_3 = tf.nn.relu(tf.add(tf.matmul(hidden_2, W_hidden_3),     
bias_hidden_3))
hidden_4 = tf.nn.relu(tf.add(tf.matmul(hidden_3, W_hidden_4), 
bias_hidden_4))

# Output layer (transpose!)
out = tf.transpose(tf.add(tf.matmul(hidden_4, W_out), bias_out))

# Cost function
mse = tf.reduce_mean(tf.squared_difference(out, Y))

# Optimizer
opt = tf.train.AdamOptimizer().minimize(mse)

# Init
net.run(tf.global_variables_initializer())

# Fit neural net
batch_size = 10
mse_train = []
mse_test = []

# Run
epochs = 10
for e in range(epochs):

# Shuffle training data
shuffle_indices = np.random.permutation(np.arange(len(y_train)))
X_train = X_train[shuffle_indices]
y_train = y_train[shuffle_indices]

# Minibatch training
for i in range(0, len(y_train) // batch_size):
    start = i * batch_size
    batch_x = X_train[start:start + batch_size]
    batch_y = y_train[start:start + batch_size]
    # Run optimizer with batch
    net.run(opt, feed_dict={X: batch_x, Y: batch_y})

    # Show progress
    if np.mod(i, 50) == 0:


        mse_train.append(net.run(mse, feed_dict={X: X_train, Y: y_train}))
        mse_test.append(net.run(mse, feed_dict={X: X_test, Y: y_test}))

        pred = net.run(out, feed_dict={X: X_test})

print(pred)`

Have tried to tweak around with the number of hidden layers, number of nodes per layer, number of epochs to run and trying different activation functions and optimizers. However, I am quite new to neural networks, so there might be something very obvious that I'm missing.

Thanks in advance to anyone who managed to read through all of that.

Answer 1

It will make is much easier you you will share a small dataset that illustrate the problem. However, I will state some of the issues with non-standards datasets and how to overcome them.

Possible solutions

1. Regularization and validation-based optimization - are methods that are always good to try when looking for some extra-accuracy. See dropout methods here (original paper), and some overview here .

2. Unbalanced data - Sometimes of the time series categories/events behave like anomalies, or just in unbalanced ways. If you read a book, words like the or it will appear much more times than warehouse or such. This can become a problem if your main task is to detect the word warehouse and you train your network (even lstms) in traditional ways. A way to overcome this problem is by balancing the samples (creating balanced datasets) or to give more weight to low-frequent categories.

3. Model structure - sometimes fully connected layers are not enough. See computer vision problems for instance, where we train using convolution layers. The convolution and pooling layers enforce structure on the model, which is suitable for images. This is also some sort of regulation, since we have less parameters in those layers. In time-series problems, convolutions are also possible and turns out that works just fine. See example in Conditional Time Series Forecasting with Convolution Neural Networks .

The above suggestions are presented in the order I would suggest to try.

Good luck!