pca python

Http://matlabdatamining.blogspot.com/2010/02/principal-components-analysis.htmlEnglish principal components Analysis of the blog, write very good, worried after not open, full text reproduced.Principal Components AnalysisIntroductionReal-world data sets usually exhibit relationships among their variables. These relationships is often linear, or at least approximately so, making them amenable to common analysis techniques. One such technique isprincipal Component analysis("

dimensionality reduction (i)----the source of principal component analysis (PCA)Reduced Dimension Series: dimensionality reduction (i)----the source of principal component analysis (PCA) dimensionality Reduction (ii)----Laplacian Eigenmaps ---------------------Principal component Analysis (PCA) is introduced in many tutorials, but why is the pri

1.PCA Algorithm Overview introduction of 1.1 PCA algorithm PCA (Principal Component analysis) is a statistical process that converts a set of observation values of a possible correlation variable into a set of linearly independent variable values by means of an orthogonal transformation, known as the principal component. The number of principal components is le

PCA (Principal Component analysis) is also known as the Karhunin-low transformation (Karhunen-loeve Transform), a technique used to explore high-dimensional data structures. PCA is often used for exploration and visualization of high-dimensional datasets. can also be used for data compression, data preprocessing and so on. PCA can synthesize high-dimensional vari

needs to be represented as a vector form to be trained in the input model. However, it is well known that the processing and analysis of high-dimensional vectors can greatly consume system resources and even create dimensional disasters. For example, in the field of CV (computer vision) to extract a 100x100 RGB image pixel features, the dimension will reach 30000, in NLP (Natural language Processing) in the field of The common dimensionality reduction methods include principal component analysi

1. Principle of PCA The main component analysis is often used in the field of image processing, and the advantage is that the dimension of the data to be analyzed is reduced, but the main information of the data can be retained. It works like this, for a given set of data (column vectors): When it is centered, it is represented as: where u is the mean value of the input column vector. The central data is U1 in the first spindle (both the main di

PCA (Principal Component analysis) is a commonly used method for analyzing data. PCA transforms the original data into a set of linearly independent representations of each dimension by linear transformation, which can be used to extract the main feature components of the data, and is often used for dimensionality reduction of high dimensional data. There are many articles on

vector E, its feature value V is the weight. Now, each row vector can be written as VN = (E1 * v1n, e2 * v2n... Em * vmn), and the matrix becomes a square matrix. If the rank of the matrix is smaller, the storage of the matrix can be compressed. Furthermore, because the projection size represents the projection of each component of a in the feature space, we can use the least 2 multiplication to find the components with the largest projection energy, remove the remaining components to save the

In the preprocessing of data, we often encounter the data dimension is very large, if not the corresponding feature processing, then the resource cost of the algorithm is very large, which in many scenarios is unacceptable. However, there is often a large correlation between some dimensions of data, if the data can be processed between the dimensions, so that they retain the maximum data information while reducing the correlation between the dimensions, you can achieve the effect of dimensionali

^t\sigma v\) You can export two matrices \ (a_1=av^t=u^t\sigma=\sum_{i=1}^{r}\sigma_i u_i\) and \ (A_2=ua=\sigma v=\sum_{i=1}^{r} \sigma_i v_i^t\). The two matrices can be thought of as the \ (M\times r\) and \ (R\times n\) matrices of the original matrix \ (a\) for column/row compression. This method can be used instead of the PCA mentioned below to process the data, for example, the PCA algorithm in Sciki

The main advantages of the LDA algorithm are: prior knowledge of classes can be used in the dimensionality reduction process, while unsupervised learning such as PCA cannot use class priori knowledge. LDA is better than the PCA algorithm when it relies on the mean value instead of the variance in the sample classification information. The main drawbacks of the LDA algorithm are: L

For PCA, has always been a concept, no actual use, today finally the actual use of a, found that PCA is quite magical.The use of PCA in OpenCV is simple, as long as several statements are available.1. Initialize dataEach row represents a samplecvmat* PData = Cvcreatemat (total number of samples, number of dimensions per sample, CV_32FC1);cvmat* Pmean = Cvcreatema

PCA algorithm is also called Principal component Analysis (principal), which is mainly used for data dimensionality reduction.Why is data dimensionality reduced? Because of the fact that our training data can be characterized by too many features or a cumbersome problem, such as: A sample data about the car, one characteristic is "the maximum speed characteristic of km/h" and the other is the maximum speed characteristic of "mph", which obvio

Source: http://blog.csdn.net/zhongkelee/article/details/44064401 Reprint please declare the source: http://blog.csdn.net/zhongkelee/article/details/44064401 A brief introduction of PCA 1. Related background After Chenhonghong teacher's "machine learning and Knowledge discovery" and Tihaibo Teacher's "matrix algebra" two courses, quite experience. Recently in the master component analysis and singular value decomposition of the project, so record the

Principle:Principal component Analysis-Stanford Principal component Analysis Method-think tank Principle of PCA (Principal Component analysis) Principal component Analysis and R language case-Library Principle application and calculation steps of principal component analysis Method-Library Main component analysis of the R chapter Five questions about principal component analysis Multivariate statistical methods, through the main components of the anal

Http://blog.sina.com.cn/s/blog_5d793ffc0100g240.html Later, sift had two extensions that used the PCA concept.1 PCA-SIFT The PCA-SIFT has the same sub-pixel location (sub-pixel), scale, and dominant orientations as the standard sift, but when the description is calculated in step 1, it uses 41 × 41 image spots around the feature points to calculate its principal

Singular Value Decomposition and application (PCA LSA), decomposing pca I have saved a lot of mathematical knowledge here. It is recommended that readers with weak mathematics should first look at Chapter 18th of PCA: For details about PCA, see http://blog.csdn.net/lu597203933/article/details/42544547. Here we mainly

information.Many of the features here are related to class labels, but there is noise or redundancy. In this case, a feature reduction method is required to reduce the number of features, reduce noise and redundancy, and reduce the likelihood of overfitting.A method called Principal component Analysis (PCA) is discussed below to solve some of the above problems. The idea of PCA is to map n-dimensional feat

Step 0: load data The starter Code contains code to load 45 2D data points. When plotted usingScatterFunction, the results shocould look like the following: Step 1: Implement PCA In this step, you will implement PCA to obtainXROT, The matrix in which the data is "rotated" to the basis comprising made up of the principal components Step 1a: finding the PCA