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Machine Learning 4, machine learning
Probability-based classification method: Naive BayesBayesian decision theory
Naive Bayes is a part of Bayesian decision-making theory. Therefore, before explaining Naive Bayes, let's take a quick look at Bayesian decision-making theory knowledge.
The core idea of Bayesian decision-m
p.s. SVM is more complex, the code is not studied clearly, further learning other knowledge after the supplement. The following is only the core of the knowledge, from the "machine learning Combat" learning summary. Advantages:The generalization error rate is low, the calculation cost is small, the result is easy to ex
extension, decision tree, neural network, SVM of support vector machine, rule learning, etc.If it is a regression problem, it can be considered as a continuous form of classification by means of variants or extensions of the above model.If the probability is involved, we can refer to the neural network, Bayesian, maximum likelihood, EM, probability graph, hidden Markov model, reinforcement
(Np.float)
# This are important from
sklearn.preprocessing import standardscaler
scaler = Standardscaler ()
X = Scaler.fit_transform (X)
print "Feature space holds%d observations and%d features"% X.sha PE
print "Unique target labels:", Np.unique (y)
Many predictive variables care about the relative size of different features, even if these scales may be arbitrary. For example: The basketball team scored more points in each game than they were in a few orders of magnitude. But that does not
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better (3)Machine learning Cornerstone Note 16--Machine How to learn better (4)XV, ValidationVerify.15.1 Model Selection problemModel selection issues.So far, many algorithmic models have been learned, but a model requires a lot of parameter selection, which is the focus of this chapter's discussion.Taking the two-yua
Cross entropy cost function 1. Cross-entropy theory
Cross entropy is relative to entropy, as covariance and variance.
Entropy examines the expectation of a single information (distribution):
H (p) =−∑I=1NP (xi) Logp (xi)
Cross-Entropy examines the expectations of two of information (distributions):H (P,Q) =−∑I=1NP (xi) logq (xi)For details, please see Wiki Cross entropy
y = Tf.placeholder (Dtype=tf.float32, Shape=[none, ten]) ...
Scores = Tf.matmul (H, W) + b
probs = Tf.nn.softmax (scores)
l
1. Vector Norm
Norm, Norm, is a concept similar to "Length" in mathematics, which is actually a kind of function.The regularization (regularization) and sparse coding (Sparse coding) in machine learning are very interesting applications.For Vector a∈rn A\in r^n, its LP norm is | | a| | p= (∑IN|AI|P) 1p (1) | | a| | _p= (\sum_i^n |a_i|^p) ^{\frac 1 p} \tag 1Commonly used are:
L0 NormThe number of elements i
the concepts of "multilevel", "adaptive" and "average" to simplify the research ideas and ideas behind the numerous and colorful machine learning models and computational methods. Hopefully, this will inspire you to understand some of the models, methods, and future research that machine learning already has.1. Multil
is all 0. And because it can be deduced that b=1nz∗zt=wt∗ (1NX∗XT) w=wt∗c∗w, this expression actually means that the function of the linear transformation matrix W in the PCA algorithm is to diagonalization the original covariance matrix C. Because diagonalization in linear algebra is obtained by solving eigenvalue and corresponding eigenvector, the process of PCA algorithm can be introduced (the process is mainly excerpted from Zhou Zhihua's "machine
of the current node is the middle half of the distance of all its leaf nodes is float (NUMLEAFS)/2.0/plottree.totalw* 1, but since the start Plottree.xoff assignment is not starting from 0, but the left half of the table, so also need to add half the table distance is 1/2/plottree.totalw*1, then add up is (1.0 + float (numleafs))/2.0/ Plottree.totalw*1, so the offset is determined, then the X position becomes Plottree.xoff + (1.0 + float (numleafs))/2.0/PLOTTREE.TOTALW3, for Plottree function
first, gradient descent method
In the machine learning algorithm, for many supervised learning models, the loss function of the original model needs to be constructed, then the loss function is optimized by the optimization algorithm in order to find the optimal parameter. In the optimization algorithm of
Brief introduction:Support Vector Machine (SVM) is a supervised learning model of two classification, and his basic model is a linear model that defines the largest interval in the feature space. The difference between him and the Perceptron is that the perceptron simply finds the hyper-plane that can divide the data correctly, and SVM needs to find the most spaced hyper-plane to divide the data. So the per
-1 when you mistakenly classify, then you judge +1, then calculate (w*x0+b>0), so meet -yi (w*x+b) >0
Then we can remove the absolute value symbol and get the distance of the wrong classification point:
Because you know, you can simply remove the absolute value. Then you can get the total distance (where m is the number of the wrong classification points):
In this way, we get the initial loss function of the perceptual machine model.
Without consid
Gradient descent algorithm minimization of cost function J gradient descent
Using the whole machine learning minimization first look at the General J () function problem
We have J (θ0,θ1) we want to get min J (θ0,θ1) gradient drop for more general functions
J (Θ0,θ1,θ2 .....) θn) min J (θ0,θ1,θ2 .....) Θn) How this algorithm works. : Starting from the initial assumption
Starting from 0, 0 (or any other valu
Python machine learning Chinese version, python machine Chinese Version
Introduction to Python Machine Learning
Chapter 1 Let computers learn from data
Convert data into knowledge
Three types of machine
. Because the decision tree is ultimately based on a single condition at the bottom, an attacker often needs to change a few features to escape monitoring.
Constrained by its simplicity, the greater usefulness of decision trees is the cornerstone of some more useful algorithms.Random Forest (Random forest)
When it comes to decision trees, you have to mention random forests. As the name suggests, the forest is a lot of trees.
Strictly speaking, random forest is actually an integration algorithm.
Experimental purposes
Recently intend to systematically start learning machine learning, bought a few books, but also find a lot of practicing things, this series is a record of their learning process, from the most basic KNN algorithm began; experiment Introduction
Language: Python
GitHub Address: LUUUYI/KNNExperiment
, we need to readjust the target function to punish the outliers, and the second item after the objective function indicates that the more outliers, the larger the target function value, and the smaller the target functions we are asking for. Here c is the weight of outliers, the greater the C, the greater the impact of outliers on the target function, that is, the more you do not want to see outliers. At this time, the interval will also be very small. We see that the objective function control
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