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# 人脸识别 --LDA PowerPoint PPT Presentation

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## 人脸识别--LDA

LDA算法介绍

PCA

LDA

### Linear Discriminant Analysis

• LDA: 找一个数学变换，使得投影后同类样本的特征分布仅可能紧密，不同类样本的特征分布尽可能远离。

1 2 3 …… C

1

Ni

class1

y

class2

x

1：则第i类人脸的均值则为：

2：所有人脸的均值：

3：则类内散度矩阵可以表示为：

4：则类间散度矩阵可以表示为：

### Linear Discriminant Analysis

Question?

• LDA: 找一个数学变换，使得投影后同类样本的特征分布仅可能紧密，

• 不同类样本的特征分布尽可能远离。

projection matrix

：x经过投影后得到数据y的散度矩阵

How?

### LDA vs PCA

Is LDAalways better than PCA？

• There has been a tendency in the computer vision community to prefer LDA over PCA.

• This is mainly because LDA deals directly with discrimination between classes while PCA does not pay attention to the underlying class structure.

• Main results of this study:

(1) When the training set is small, PCA can outperform LDA.

(2) When the number of samples is large and representative for each class, LDA outperforms PCA.

### 人脸识别产品分析

1：软件或者硬件

2：SDK或者API Service

30-80cm

1.嫌疑人识别

2.陌生人识别

Thank You !

iiec.cqu.edu.cn