Background
A typical correlation analysis (CCA) investigated the linear correlation between two sets of data. The CCA may linearly project two sets of random variables into a low-dimensional subspace with the greatest correlation. Researchers use CCA to simultaneously reduce the dimensions of two sets of feature vectors (i.e., two views) to obtain two low-dimensional feature representations, which are then effectively fused to form discriminative features, thereby improving the classification accuracy of patterns. Because the CCA method is simple and effective, the CCA method has wide application in blind source separation, computer vision, voice recognition and the like.
The canonical correlation analysis is an unsupervised linear learning method. However, in real life there are situations where the dependency between two views cannot be simply represented linearly. If there is a non-linear relationship between the two views, it is not appropriate to still handle the CCA method in this case. The proposal of Kernel Canonical Correlation Analysis (KCCA) effectively solves the nonlinear problem. KCCA is a nonlinear extension of CCA and has a good effect in dealing with simple nonlinear problems. When more complex non-linear problems are encountered, Deep canonical correlation analysis (Deep CCA) may better address such problems. Deep CCA combines a Deep neural network with CCA, and can learn a complex nonlinear relationship of two view data. From another perspective of non-linear expansion, the idea of locality can be incorporated into CCA, and a Locality Preserving Canonical Correlation Analysis (LPCCA) method arises. The LPCCA can find a local manifold structure of each view data to visualize the data.
Although the CCA has a good recognition effect on some pattern recognition problems, it is an unsupervised learning method and does not fully use class label information, which not only causes resource waste, but also reduces the recognition effect. To address this problem, researchers have proposed Discriminant Canonical Correlation Analysis (DCCA) that takes into account the inter-class and intra-class information of the sample. The DCCA method enables the correlation degree between the sample characteristics of the same category to be maximum, and the correlation degree between the sample characteristics of different categories to be minimum, so that the accuracy of mode classification can be improved.
The above methods are all methods suitable for analyzing the relationship between two views, and the application of the above methods is limited when there are three or more views. The multiple-set canonical correlation analysis (MCCA) method is a multi-view extension of the CCA method. The MCCA not only reserves the characteristic of maximum correlation degree between the CCA views, but also makes up the defect that the CCA cannot be applied to a plurality of views, and improves the identification performance of the CCA method. Researchers combine MCCA and DCCA, and have proposed discrimination multiple set canonical correlation analysis (DMCCA), and experiments prove that the method has better recognition performance in the aspects of face recognition, handwritten number recognition, emotion recognition and the like.
When noise interference exists or training samples are few, the auto-covariance matrix and the cross-covariance matrix in the CCA deviate from the true values, resulting in poor final recognition. In order to solve the problem, researchers combine the fractional order thought with CCA, reconstruct an auto-covariance matrix and a cross-covariance matrix by introducing a fractional order parameter, and provide typical correlation analysis of fractional order embedding, so that the influence caused by the deviation is weakened, and the identification performance of the method is improved.
The traditional typical correlation analysis mainly studies the correlation between two views, is an unsupervised learning method, does not consider class label information, and cannot directly process high-dimensional data of more than two views.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, provides a supervision multi-set correlation feature fusion method (FDMCCA) based on spectral reconstruction, can effectively process the problem of multi-view feature fusion, simultaneously weakens the influence caused by noise interference and limited training samples due to the introduction of fractional order parameters, and improves the accuracy of system identification.
The purpose of the invention is realized as follows: a supervised multi-set correlation feature fusion method based on spectral reconstruction comprises the following steps:
step 1) assume that there are P groups of training samples, with the mean of each group of samples being 0 and the number of classes being c, as follows:
wherein
Denotes the kth sample, m, of the jth class in the ith group
iCharacteristic dimension, n, representing the ith data set
jRepresenting the j-th class sample number, and defining the projection direction of the training sample set as
Step 2) calculating an intra-class correlation matrix of the interclass training samples
Sum auto-covariance matrix
Wherein
A matrix representing each element as 1;
step 3) for the inter-group intra-class correlation matrix obtained in step 2)
Performing singular value decomposition to obtain left and right singular vector matrixes, singular value matrixes and auto-covariance matrixes C
iiPerforming eigenvalue decomposition to obtain an eigenvector matrix and an eigenvalue matrix;
step 4) selecting proper fractional order parameters alpha and beta, re-assigning the singular value matrix and the eigenvalue matrix obtained in the step 3), and constructing a fractional order inter-class correlation matrix
And fractional order auto-covariance matrix
Step 5) constructing an optimized model of FDMCCA as
Wherein
Introducing a Lagrange multiplier method to obtain a generalized characteristic value problem E omega which is mu F omega, calculating a projection direction omega, wherein mu is a characteristic value,
step 6) considering the situation that the autocovariance matrix may be a singular matrix, introducing a regularization parameter eta on the basis of the step 5), and establishing an optimization model under the regularization as
The Lagrange multiplier method is introduced to obtain the following generalizedProblem of eigenvalue:
wherein
Is of size m
i×m
i1,2, …, P;
step 7) solving eigenvectors corresponding to the first d maximum eigenvalues according to the generalized eigenvalue problem in the step 6), thereby forming a projection matrix W of each group of datai=[ωi1,ωi2,…,ωid],i=1,2,…,P,d≤min{m1,…,mP};
Step 8) utilizing the projection matrix W of each group of dataiRespectively calculating the low-dimensional projection of each group of training samples and testing samples, and then forming fusion features finally used for classification by adopting a serial feature fusion strategy; and calculating the recognition rate.
Further, the correlation matrix in the inter-pair inter-class in step 3)
Singular value decomposition and auto-covariance matrix C
iiThe characteristic value decomposition comprises the following steps:
step 3-1) to the inter-group intra-class correlation matrix
Singular value decomposition is carried out:
wherein
And
are respectively
The left and right singular vector matrices of (a),
is that
A diagonal matrix of singular values of, and
step 3-2) on the autocovariance matrix CiiAnd (3) carrying out characteristic value decomposition:
wherein
Is C
iiThe matrix of feature vectors of (a) is,
is C
iiAnd r, and r
i=rank(C
ii)。
Further, the step 4) of constructing the fractional order inter-class correlation matrix
And fractional order auto-covariance matrix
Comprises the following steps:
step 4-1) assuming alpha is a fraction and satisfying 0 ≦ alpha ≦ 1, defining a fractional order intra-class correlation matrix
Comprises the following steps:
wherein
U
ijAnd V
ijAnd r
ijThe definition is given in step 3-1).
Step 4-2) assuming that beta is a fraction and satisfying that beta is more than or equal to 0 and less than or equal to 1, defining a fractional order auto-covariance matrix
Comprises the following steps:
wherein
Q
iAnd r
iThe definition of (3) is given in step 3-2).
Compared with the prior art, the invention has the beneficial effects that: on the basis of canonical correlation analysis, combining fractional order embedded canonical correlation analysis (FECCA) with discrimination multiple sets canonical correlation analysis (DMCCA), fully utilizing class label information, being capable of processing information fusion problems of more than two views, being applicable to multi-view feature fusion, reducing influence caused by noise interference and limited training samples due to introduction of fractional order parameters, and improving accuracy of face recognition; when the number of training samples is small, the method has a good identification effect; feature fusion for dimensionality reduction and multiple views; because the information of the class labels is carried, the identification effect of the method is superior to that of other methods in the same class method.
Detailed Description
As shown in fig. 1, a supervised multi-set correlation feature fusion method based on spectral reconstruction is characterized by comprising the following steps:
step 1) assume that there are P sets of training samples with a mean of 0 and a number of classes c for each set of samples, as follows
Wherein
Denotes the kth sample, m, of the jth class in the ith group
iCharacteristic dimension, n, representing the ith data set
jRepresenting the j-th class sample number, and defining the projection direction of the training sample set as
Step 2) calculating an intra-class correlation matrix of the interclass training samples
Sum auto-covariance matrix
Wherein
A matrix representing each element as 1;
step 3) for the inter-group intra-class correlation matrix obtained in step 2)
Performing singular value decomposition to obtain left and right singular vector matrixes, singular value matrixes and auto-covariance matrixes C
iiPerforming eigenvalue decomposition to obtain an eigenvector matrix and an eigenvalue matrix;
step 3-1) to the inter-group intra-class correlation matrix
Singular value decomposition is carried out:
wherein
And
are respectively
The left and right singular vector matrices of (a),
is that
A diagonal matrix of singular values of, and
step 3-2) on the autocovariance matrix CiiAnd (3) carrying out characteristic value decomposition:
wherein
Is C
iiThe matrix of feature vectors of (a) is,
is C
iiAnd r, and r
i=rank(C
ii)。
Step 4) selecting proper fractional order parameters alpha and beta, re-assigning the singular value matrix and the eigenvalue matrix obtained in the step 3), and constructing a fractional order inter-class correlation matrix
And fractional order auto-covariance matrix
Step 4-1) assuming alpha is a fraction and satisfying 0 ≦ alpha ≦ 1, defining a fractional order intra-class correlation matrix
Comprises the following steps:
wherein
U
ijAnd V
ijAnd r
ijThe definition is given in step 3-1);
step 4-2) assuming that beta is a fraction and satisfying that beta is more than or equal to 0 and less than or equal to 1, defining a fractional order auto-covariance matrix
Comprises the following steps:
wherein
Q
iAnd r
iThe definition of (3) is given in step 3-2).
Step 5) constructing an optimized model of FDMCCA as
Wherein
Introducing a Lagrange multiplier method to obtain a generalized characteristic value problem E omega which is mu F omega, calculating a projection direction omega, wherein mu is a characteristic value,
step 6) considering the situation that the autocovariance matrix may be a singular matrix, introducing a regularization parameter eta on the basis of the step 5), and establishing an optimization model under the regularization as
A Lagrange multiplier method is introduced to obtain the following generalized eigenvalue problem:
wherein
Is of size m
i×m
i1,2, …, P;
step 7) solving eigenvectors corresponding to the first d maximum eigenvalues according to the generalized eigenvalue problem in the step 6), thereby forming a projection matrix W of each group of datai=[ωi1,ωi2,…,ωid],i=1,2,…,P,d≤min{m1,…,mP};
Step 8) utilizing the projection matrix W of each group of dataiRespectively calculating the low-dimensional projection of each group of training samples and testing samples, and then forming fusion features finally used for classification by adopting a serial feature fusion strategy; and calculating the recognition rate.
The invention can be further illustrated by the following examples: taking the CMU-PIE face database as an example, the CMU-PIE face database contains face images of 68 persons, and the size of each image is 64 × 64. In this experiment, the first 10 images of each person were used as a training set and the second 14 images were used as a testing set. Reading input face image data to form three different features, namely: feature 1 is the original image data, feature 2 is the median filtered image data, and feature 3 is the mean filtered image data. The dimensionality of each feature is reduced using principal component analysis to form the final three sets of feature data.
Step 1) constructing three groups of data X with the average value of 0
iI-1, 2,3, defining the projection direction of the training sample set as
Step 2) FDMCCA aims to maximize the correlation of samples within a class and minimize the correlation of samples between classes. Computing intra-class correlation matrices for interclass training samples
Sum auto-covariance matrix
Wherein
A matrix representing each element as 1;
step 3) for the inter-group intra-class correlation matrix obtained in step 2)
Performing singular value decomposition to obtain left and right singular vector matrixes, singular value matrixes and auto-covariance matrixes C
iiPerforming eigenvalue decomposition to obtain an eigenvector matrix and an eigenvalue matrix;
step 3-1) to the inter-group intra-class correlation matrix
Singular value decomposition is carried out:
wherein
And
are respectively
The left and right singular vector matrices of (a),
is that
A diagonal matrix of singular values of, and
step 3-2) on the autocovariance matrix CiiAnd (3) carrying out characteristic value decomposition:
wherein
Is C
iiThe matrix of feature vectors of (a) is,
is C
iiAnd r, and r
i=rank(C
ii)。
Step 4) defining the value ranges of the fractional order parameters alpha and beta as {0.1,0.2, …,1}, selecting proper fractional order parameters alpha and beta, re-assigning the singular value matrix and the characteristic value matrix obtained in the step 3), and constructing the intra-class correlation matrix among the fractional order groups
And fractional order auto-covariance matrix
Step 4-1) assuming alpha is a fraction and satisfying 0 ≦ alpha ≦ 1, defining a fractional order intra-class correlation matrix
Comprises the following steps:
wherein
U
ijAnd V
ijAnd r
ijThe definition is given in step 3-1).
Step 4-2) assuming that beta is a fraction and satisfying that beta is more than or equal to 0 and less than or equal to 1, defining a fractional order auto-covariance matrix
Comprises the following steps:
wherein
Q
iAnd r
iThe definition of (3) is given in step 3-2).
Step 5) constructing an optimized model of FDMCCA as
Wherein
The Lagrange multiplier method is introduced to obtain the generalized characteristicsThe value problem E ω ═ μ F ω, and the projection direction ω is then determined, where
Step 6) considering the situation that the autocovariance matrix may be a singular matrix, introducing a regularization parameter eta on the basis of the step 5), wherein the eta value range is {10 }
-5,10
-4…,10}, establishing an optimization model under regularization as
The following generalized eigenvalue problem can be obtained by introducing the Lagrange multiplier method:
and 7) solving a projection direction omega according to the generalized characteristic value problem in the step 6), calculating the projection of the test sample in the projection direction, adopting a serial characteristic fusion strategy, classifying by using a nearest neighbor classifier, and calculating the recognition rate. Solving eigenvectors corresponding to the first d maximum eigenvalues according to the generalized eigenvalue problem in the step 6), thereby forming a projection matrix W of each group of datai=[ωi1,ωi2,…,ωid],i=1,2,3,d≤min{m1,m2,m3};
Step 8) utilizing the projection matrix W of each group of dataiRespectively calculating the low-dimensional projection of each group of training samples and testing samples, and then forming fusion features finally used for classification by adopting a serial feature fusion strategy; and classifying by using a nearest neighbor classifier, and calculating the recognition rate. The recognition results are shown in table 1 and fig. 2 (BASELINE refers to the classification results after three features are connected in series). As can be seen from table 1 and fig. 2, the FDMCCA method proposed by the present invention is superior in effect to other methods. This is because: compared with MCCA, CCA and BASELINE, FDMCCA is a supervised learning method with prior information and can obtain better identification effect. Andcompared with DMCCA, FDMCCA introduces fractional order thought to correct covariance deviation caused by noise interference and other factors, and identification accuracy is improved.
TABLE 1 recognition Rate on CMU-PIE datasets
Method
|
Percent identification (%)
|
MCCA
|
84.09
|
CCA (feature 1+ feature 2)
|
71.43
|
CCA (feature 1+ feature 3)
|
74.03
|
CCA (feature 2+ feature 3)
|
76.30
|
BASELINE
|
48.05
|
DMCCA
|
79.22
|
FDMCCA
|
86.04 |
In order to examine the influence of the number of training samples on the recognition rate, the fractional order parameters alpha and beta and the regularization parameter eta are fixed, different numbers of images are selected to be respectively used as a training set and a test set, and the recognition rate is shown in FIG. 3. As can be seen from fig. 3, the FDMCCA works better with fewer training samples.
In summary, the present invention provides a supervised multi-set correlation feature fusion method (FDMCCA) based on spectral reconstruction by introducing a fractional order embedding concept based on the CCA method. The method can correct the deviation of the intra-class correlation matrix and the auto-covariance matrix caused by noise interference and limited training samples by introducing the fractional order parameter. Meanwhile, the method makes full use of the class label information, can solve the problem of information fusion of more than two views, and has wider application range and better identification performance.
The present invention is not limited to the above-mentioned embodiments, and based on the technical solutions disclosed in the present invention, those skilled in the art can make some substitutions and modifications to some technical features without creative efforts according to the disclosed technical contents, and these substitutions and modifications are all within the protection scope of the present invention.