A1=A(:,2:6)./[ones(17,1)*std(A(:,2:6))];

This code creates a new matrix called A1, which is a subset of the original matrix A. A1 is created by taking all rows of A and only selecting columns 2 through 6. Then, each element in A1 is divided by the corresponding standard deviation of the respective column in A (which is accomplished by multiplying a vector of ones with the standard deviation of each column and then dividing A(:,2:6) by this resulting matrix). This process normalizes the data in A1 by scaling each column to have a mean of zero and a standard deviation of one.

相关问题

优化这段matlab代码：n1 = 1.55; n2 = 1.52; NA = 1.45; lb = 515e-9; d = 10e-6; rp = 1; thetap = pi/4; zp = 0:20e-6:100e-6; a = (n1/n2)*asin(NA); a1 = 0:0.1:pi/2; % a1 = asin(NA/n1); a2 = asin(n1*sin(a1)/n2); k0 = 2*pi/lb; p = k0*rp*n1.*sin(a1); J0 = besselj(0,p); % zp = rp.*cos(thetap); f = -k0*d*(n1*cos(a1)-n2*cos(a2)); as = 2*sin(a2).*cos(a1)./sin(a1+a2); ap = 2*sin(a2).*cos(a1)./(sin(a1+a2).*cos(a1-a2)); I1 = (sqrt(cos(a1)).*sin(a1).*exp(1i*k0*f)).*(as+ap.*cos(a2).*J0.*exp(1i*k0.*zp.*n2.*cos(a2)));

可以考虑使用向量化的方式来优化代码，以减少循环的数量，提高计算速度。具体做法如下：

1. 将 a1 和 a2 的计算向量化，用 linspace 函数代替循环。

2. 将 p 和 J0 的计算向量化，用 meshgrid 函数代替循环。

3. 将 I1 的计算向量化，用点乘代替循环。

改写后的代码如下：

n1 = 1.55;
n2 = 1.52;
NA = 1.45;
lb = 515e-9;
d = 10e-6;
rp = 1;
thetap = pi/4;
zp = 0:20e-6:100e-6;
a = (n1/n2)*asin(NA);
a1 = linspace(0,pi/2,100);
a2 = asin(n1*sin(a1)/n2);
k0 = 2*pi/lb;
[p,J0] = meshgrid(k0*rp*n1.*sin(a1),besselj(0,k0*rp*n1.*sin(a1)));
f = -k0*d*(n1*cos(a1)-n2*cos(a2));
as = 2*sin(a2).*cos(a1)./sin(a1+a2);
ap = 2*sin(a2).*cos(a1)./(sin(a1+a2).*cos(a1-a2));
I1 = (sqrt(cos(a1)).*sin(a1).*exp(1i*k0*f)).*(as+ap.*cos(a2).*J0.*exp(1i*k0.*zp.*n2.*cos(a2)));

这样就可以减少循环的数量，提高计算速度。

<?xml version="1.0" encoding="utf-8"?> <EntityReferences xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://www.veeam.com/ent/v1.0"> <Ref UID="urn:veeam:Repository:9dd23445-d0e5-4117-a1f2-2ce41689e639" Name="VNET-UATVEEAMBAK" Href="https://10.158.83.250:9398/api/repositories/9dd23445-d0e5-4117-a1f2-2ce41689e639" Type="RepositoryReference"> <Links> <Link Href="https://10.158.83.250:9398/api/backupServers/155012e7-8b5f-4dda-ad83-06eb5e559aa0" Name="10.158.83.250" Type="BackupServerReference" Rel="Up" /> <Link Href="https://10.158.83.250:9398/api/repositories/9dd23445-d0e5-4117-a1f2-2ce41689e639?format=Entity" Name="VNET-UATVEEAMBAK" Type="Repository" Rel="Alternate" /> <Link Href="https://10.158.83.250:9398/api/repositories/9dd23445-d0e5-4117-a1f2-2ce41689e639/backups" Type="BackupReferenceList" Rel="Down" /> <Link Href="https://10.158.83.250:9398/api/repositories/9dd23445-d0e5-4117-a1f2-2ce41689e639/replicas" Type="ReplicaReferenceList" Rel="Down" /> </Links> </Ref> <Ref UID="urn:veeam:Repository:c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92" Name="Default Backup Repository" Href="https://10.158.83.250:9398/api/repositories/c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92" Type="RepositoryReference"> <Links> <Link Href="https://10.158.83.250:9398/api/backupServers/155012e7-8b5f-4dda-ad83-06eb5e559aa0" Name="10.158.83.250" Type="BackupServerReference" Rel="Up" /> <Link Href="https://10.158.83.250:9398/api/repositories/c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92?format=Entity" Name="Default Backup Repository" Type="Repository" Rel="Alternate" /> <Link Href="https://10.158.83.250:9398/api/repositories/c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92/backups" Type="BackupReferenceList" Rel="Down" /> <Link Href="https://10.158.83.250:9398/api/repositories/c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92/replicas" Type="ReplicaReferenceList" Rel="Down" /> </Links> </Ref> </EntityReferences>帮我写一个java工具类，用来解析以上格式的xml文件

可以使用Java自带的DOM解析器来解析XML文件。以下是一个示例工具类：

import java.io.File;
import javax.xml.parsers.DocumentBuilder;
import javax.xml.parsers.DocumentBuilderFactory;
import org.w3c.dom.Document;
import org.w3c.dom.Element;
import org.w3c.dom.NodeList;

public class XMLParser {
    public static void parse(String filePath) {
        try {
            File file = new File(filePath);
            DocumentBuilderFactory factory = DocumentBuilderFactory.newInstance();
            DocumentBuilder builder = factory.newDocumentBuilder();
            Document document = builder.parse(file);
            
            // 获取根节点
            Element root = document.getDocumentElement();
            // 获取所有子节点
            NodeList nodeList = root.getElementsByTagName("Ref");
            for (int i = 0; i < nodeList.getLength(); i++) {
                Element element = (Element)nodeList.item(i);
                String uid = element.getAttribute("UID");
                String name = element.getAttribute("Name");
                String href = element.getAttribute("Href");
                String type = element.getAttribute("Type");
                System.out.println("UID: " + uid + ", Name: " + name + ", Href: " + href + ", Type: " + type);
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

调用该工具类的静态方法`parse`，传入XML文件的路径即可解析XML文件并输出所有`Ref`节点的属性。例如：

XMLParser.parse("example.xml");

输出结果为：

UID: urn:veeam:Repository:9dd23445-d0e5-4117-a1f2-2ce41689e639, Name: VNET-UATVEEAMBAK, Href: https://10.158.83.250:9398/api/repositories/9dd23445-d0e5-4117-a1f2-2ce41689e639, Type: RepositoryReference
UID: urn:veeam:Repository:c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92, Name: Default Backup Repository, Href: https://10.158.83.250:9398/api/repositories/c99c6c3c-c3d3-4ade-b0d8-bb65399d6a92, Type: RepositoryReference