多元函数微分：矩阵力量与机器学习进阶

需积分: 5 0 下载量 70 浏览量 更新于2024-06-21 收藏 1.02MB PDF 举报
在Book4第17章"多元函数微分：矩阵力量，从加减乘除到机器学习"中，作者深入探讨了在多维度空间中的函数微分理论，扩展了单变量微分的概念，重点涉及以下几个关键知识点： 1. **多元函数的导数**：章节首先介绍了多元函数的偏导数，这是对多变量函数在不同变量上的局部变化率的分析。作者通过numpy库中的meshgrid()函数生成网格数据，以便更好地理解函数在多维空间中的行为。 2. **向量和矩阵运算**：numpy的multiply()函数用于执行元素级别的乘法，这对于计算偏导数时的向量和矩阵乘法至关重要。同时，numpy.roots()用于求解多项式的根，sqrt()函数则处理开平方操作。 3. **符号计算工具**：sympy库被用来处理符号计算，如sympy.abc导入符号变量x，sympy.diff()用于求解符号导数和偏导数的解析表达式，而sympy.Eq()定义符号等式，sympy.evalf()则用于将符号解析式中的变量替换为具体数值。 4. **可视化技术**：隐函数的绘图是理解和展示多元函数的重要手段，sympy.plot_implicit()用于绘制隐函数方程，帮助读者直观地理解多元函数的特性。 5. **梯度、黑塞矩阵与法向量**：核心概念包括梯度向量，它代表了函数值变化最快的方向，黑塞矩阵（Hessian Matrix）用于衡量各偏导数的交互作用，法向量则在多元函数曲面的切线上，指示了最大或最小值的方向。 6. **几何视角**：章节讨论了这些数学概念如何应用于几何解析，比如在理解多元函数曲面的形状、极值点及其性质时，这些概念显得尤为关键。 本章内容旨在为读者提供深入理解多元函数微分的理论框架，以及如何运用这些理论解决实际问题，例如在机器学习中的梯度下降法和优化算法。作者强调了代码示例和实践应用的重要性，并鼓励读者通过配套微课视频（生姜DrGinger在B站）和专属邮箱获取更多指导和反馈。最终，所有内容都基于清华大学出版社的出版标准，提醒读者引用时要尊重版权。

JSON_OBJECT(OLD.ID, OLD.BUSINESS_ID, OLD.APPLICATION_DATE , OLD.FINISH_DATE, OLD.LINKMAN_ID, OLD.TOMB_ID, OLD.TOMB_STONE_ID, OLD.ASH_BUSINESS_ID,OLD.REGISTER_USER, OLD.REGISTER_USER_NAME, OLD.REGISTER_DATE, OLD.DEPT_ID, OLD.DEPT_NAME, OLD.`STATUS`, OLD.BOOK_ID, OLD.BUSINESS_VERSION, OLD.IS_CREATEWORK, OLD.IS_SENDCUSTOMER, OLD.SEND_USER, OLD.SEND_DATE, OLD.USER_NAME, OLD.TOMB_DESIGNER, OLD.TOMB_DESIGNER_ID, OLD.DESIGN_START_DATE, OLD.DESIGN_END_DATE, OLD.TOMB_CERTIFICATE_NO, OLD.CONTRACT_NO, OLD.CONTRACT_PRINT_NUM, OLD.CUSTOMER_LOCK, OLD.CUSTOMER_USER, OLD.CUSTOMER_DATE, OLD.PRE_BOOK_ID, OLD.EARNEST_DATE, OLD.PAYOFF_DATE, OLD.INVOICE_DATE, OLD.LINKMAN_NAME, OLD.VALIDATE_DATE, OLD.LAYER_CODE_NEW2, OLD.BURY_DATE_REMARK, OLD.DESIGN_DATE_REMARK, OLD.OLD_TOMB_ID, OLD.CONTRACT_DATE, OLD.LINKMAN_BEFORE_ID, OLD.IF_SAVE, OLD.COLLECT_VERSION)优化一下

2023-06-13 上传
'book_id', OLD.BOOK_ID, 'business_version', OLD.BUSINESS_VERSION, 'is_creatework', OLD.IS_CREATEWORK, 'is_sendcustomer', OLD.IS_SENDCUSTOMER, 'send_user', OLD.SEND_USER, 'send_date', OLD.SEND_...

select o.order_num,o.start_time,o.total,bk.book_name,bk.book_price,od.num,od.total from order o inner join order_detail od on o.order_id=od.order_id where o.user_id=1008611 inner join book bk on od.book_id=bk.book_id;

2023-06-08 上传
INNER JOIN book bk ON od.book_id = bk.book_id WHERE o.user_id = 1008611; ``` 注意，`order` 是 MySQL 中的保留关键字，因此需要使用反引号将其括起来以避免语法错误。同时，建议使用表的别名以简化 SQL 语句的...

public class BookDaoTest { @Test public void testAddBook() { //创建一个Book对象 Book book = new Book(); book.setBook_ISBN("456"); book.setBook_category("计算机科学"); book.setBook_name("java编程思想"); book.setBook_author("张三"); book.setPublish_house("机械工业出版社"); book.setPublish_time("2020-01"); book.setBook_price(65); book.setBook_sum(10); book.setBook_remain(2); book.setBook_introduce("无"); //调用addBook方法 BookDao bookDao = new BookDao(); bookDao.addBook(book); //获取添加后的图书信息 String sql = "select * from Book where book_ISBN=?"; Object[] params = { "456" }; ResultSet rs = DBHelper.executeQuery(sql, params); // 检查添加的图书信息是否正确 assertEquals("456", ((Book) rs).getBook_ISBN()); assertEquals("计算机科学", ((Book) rs).getBook_category()); assertEquals("java编程思想", ((Book) rs).getBook_name()); assertEquals("张三", ((Book) rs).getBook_author()); assertEquals("机械工业出版社", ((Book) rs).getPublish_house()); assertEquals("2020-01",((Book) rs).getPublish_time()); assertEquals(65, ((Book) rs).getBook_price(), 0.01); assertEquals(12, ((Book) rs).getBook_sum()); assertEquals(4, ((Book) rs).getBook_remain()); assertEquals("无", ((Book) rs).getBook_introduce()); } }怎么修改

2023-06-12 上传
因此，需要在ResultSet对象中获取正确的属性值，并将其设置到Book对象中，然后再进行比较。修改后的代码如下： ``` public class BookDaoTest { @Test public void testAddBook() { //创建一个Book对象 Book ...

优化以下SQL使其查询速度更快SELECT P.LOT_NO UNIT_ID, '0' AS UNIT_TYPE, '宗地' AS UNIT_TYPE_DES, NVL(BD.PARCEL_CODE_TMP, P.LOT_NO || P.SITE) UNIT_CODE, P.PARCEL_NO, P.LOC_CANTON, BD.REAL_UNIT_NO AS UNIT_CODE_GB, P.LU_LOCATION, P.SITE_KEY, P.CHG_TYPE, P.LU_AREA AS UNIT_AREA, P.PARCEL_CODE FROM V_LD_PARCEL P LEFT JOIN V_BD_PARCEL BD ON BD.LOT_NO = P.LOT_NO where 2 > 1 and not exists (select 1 from v_bk_reg_idx idx where idx.reg_unit_code = p.lot_no and idx.reg_unit_type = '0' and idx.buss_reg_type = '1101' and (idx.status_book = '1' or idx.status_book = '9')) and not exists(select 1 from v_bk_reg_idx idx where (idx.reg_unit_code, idx.reg_unit_type) in (select rise_id, '1' from bd_rise br, bd_parcel bp where br.par_lot_no = bp.lot_no and bp.lot_no = p.lot_no) and idx.buss_reg_type = '1200') and p.parcel_no = ?

2023-05-26 上传
AND (idx.status_book = '1' OR idx.status_book = '9') WHERE 2 > 1 AND idx.reg_unit_code IS NULL AND P.PARCEL_NO = ? ``` 同样，将第二个子查询转换为JOIN语句也可以提高性能： ``` SELECT P.LOT_NO UNIT_...

import requests import os from bs4 import BeautifulSoup class book_spider(): def __init__(self,root_url): self.root_url=root_url self.book_list=[] #一级页面中获取的数据（二级页面地址）存放于此列表 self.chapter_list=[] #二级页面中获取的数据（三级页面地址和章节名）存放于此列表 def get_url(url): while True: try: res=requests.get(url) if res.status_code==200: res.encoding =res.apparent_encoding print("页面获取成功") return res.text else: print("页面返回异常",res.status_code) except: print("页面获取错误") def get_book_list(self.url): res = self.get_url(url) html = BeautifulSoup(res,"html.parser") a_list = html.find_all("a",{"class":"name"}) for a in a_list: self.book_list.append(a["href"]) self.book_list = [self.root_url+i for i in self.bbok_list] self.book_list.remove('http://10.1.88.252:7000/庆余年') print(book_list) def get_chapter_list(self,url): res = self.get_url(url) html = BeautifulSoup(res,"html.parser") a_list = html.find_all("a",{"class":"chapter"}) for a in a_list: self.chapter_list.append((a["href"],a.text.replace("\n",""))) def get_content(self.chapter): url = self.root_url + chapter[0] print(url) book_name = chapter[0].split("/")[1] print(book_name) if not os.path.exists(book_name): os.mkdir(book_name) res = self.get_url(url) html = BeautifulSoup(res,"html.parser") content = html.find("div",{"id":"content"}).text print(content) path = os.path.join(book_name,chapter[1]) with open(path,"w",encoding="utf8") as f: f.write(content) def main(): self.get_book_list(self.root_url) for book in self.book_list: self.get_chapter_liat(book) for chapter in chapter_list: self.get_content(chapter) book_s = book_spider("http://10.1.88.252:7000") book_s.main()这是一段爬虫代码，找出里面的错误并改正

2023-06-02 上传
2. 在 `get_book_list` 方法中，`print(book_list)` 应该改为 `print(self.book_list)`，因为 `book_list` 是类成员变量。 3. 在 `get_book_list` 方法中，将 `self.bbok_list` 改为 `self.book_list`。 4. 在 `...

翻译以下代码everyone_guest_time_daily_show_pref C INNER JOIN ( SELECT COD_CUST_ID,COD_CLERK_ID,BAL_BOOK_DAILY_0 FROM everyone_guest_time_daily_show_pref WHERE ETL_LOAD_TIME = ? AND BAL_BM_TYPE_0 = 0) F ON C.COD_CUST_ID = F.COD_CUST_ID AND C.COD_CLERK_ID = F.COD_CLERK_ID SET C.BAL_BOOK_DAILY_REAL_0 = F.BAL_BOOK_DAILY_0 WHERE C.ETL_LOAD_TIME = ?

2023-07-14 上传
这段代码是一个 SQL 查询语句，它执行了一...然后，将 C.BAL_BOOK_DAILY_REAL_0 的值设置为 F.BAL_BOOK_DAILY_0，其中 C.ETL_LOAD_TIME = ?。 ``` 请注意，代码中的 `?` 是占位符，具体的值需要根据实际情况进行替换。

帮我看看这段代码为什么运行不出来import threading import time class Library(threading.Thread): def __init__(self): threading.Thread.__init__(self) self.book_num=0 def borrow(self): global book_count global lock while True: lock = threading.Lock() time.sleep(1) if book_count>0: lock.acquire() time.sleep(0.1) book_count-=1 # book_count=book_count-1 self.book_num+=1 lock.release() print(f"借走{self.book_num}本,现有图书{book_count}本") else: break def back(self): global book_count global lock while True: lock = threading.Lock() time.sleep(3) # time.sleep(0.1) lock.acquire() book_count += 1 # book_count=book_count+1 lock.release() self.book_num -= 1 print(f"归还{self.book_num}本,现有图书{book_count}本") book_count=100 result1=Library() result2=Library() result1.start() result2.start() result1.join()

2023-05-24 上传
print(f"借走{self.book_num}本,现有图书{book_count}本") self.lock.release() else: break def back(self): global book_count while True: time.sleep(3) self.lock.acquire() self.book_num -= 1 ...

帮我把一下代码设置一个合理请求头，并加入一个延时import requests import os from bs4 import BeautifulSoup class NovelDownloader: def __init__(self, root_url): self.root_url = root_url self.book_list = [] self.chapter_list = [] def get_url(self, url): while True: try: res = requests.get(url) if res.status_code == 200: print("页面获取成功！") return res.text else: print("页面返回异常！", res.status_code) except: print("页面获取错误！") def get_book_list(self): res = self.get_url(self.root_url) html = BeautifulSoup(res, "html.parser") a_list = html.find_all("a", {"class": "name"}) for a in a_list: self.book_list.append(a["href"]) self.book_list = [self.root_url + i for i in self.book_list] self.book_list.remove('http://www.biquge5200.cc/') def get_chapter_list(self, url): res = self.get_url(url) html = BeautifulSoup(res, "html.parser") a_list = html.find_all("a", {"class": "chapter"}) for a in a_list: self.chapter_list.append((a["href"], a.text.replace("\n", ""))) def get_content(self, chapter): url = self.root_url + chapter[0] print(url) book_name = chapter[0].split("/")[1] print(book_name) if not os.path.exists(book_name): os.mkdir(book_name) res = self.get_url(url) html = BeautifulSoup(res, "html.parser") content = html.find("div", {"id": "content"}).text print(content) path = os.path.join(book_name, chapter[1]) with open(path, "w", encoding="utf8") as f: f.write(content) def main(self): self.get_book_list() for book in self.book_list: self.get_chapter_list(book) for chapter in self.chapter_list: self.get_content(chapter) if __name__ == '__main__': root_url = "http://www.biquge5200.cc/" nd = NovelDownloader(root_url) nd.main()

2023-06-02 上传
from bs4 import BeautifulSoup class NovelDownloader: def __init__(self, root_url): self.root_url = root_url self.book_list = [] self.chapter_list = [] self.headers = { "User-Agent": "Mozilla/...

public void addBook(Book b){ String sql="insert into Book values('"+b.getBook_ISBN()+"','"+b.getBook_category()+"','"+b.getBook_name()+"','"+b.getBook_author()+"','"+b.getPublish_house()+"','"+b.getPublish_time()+"','"+b.getBook_price()+"','"+b.getBook_sum()+"','"+b.getBook_remain()+"','"+b.getBook_introduce()+"')"; Object params[]={b.getBook_ISBN(),b.getBook_category(),b.getBook_name(),b.getBook_author(),b.getPublish_house(),b.getPublish_time(),b.getBook_price(),b.getBook_sum(),b.getBook_sum(),b.getBook_remain(),b.getBook_introduce()}; DBHelper.executeUpdate(sql,params); }实现junit测试的代码

2023-06-11 上传
book.getPublish_house(), book.getPublish_time(), book.getBook_price(), book.getBook_sum(), book.getBook_remain(), book.getBook_introduce()); // 使用when和thenReturn方法模拟executeUpdate返回值 ...

String sql = "select * from Book where book_ISBN=?"; Object[] params = { "456" }; ResultSet rs = DBHelper.executeQuery(sql, params); // 检查添加的图书信息是否正确 assertEquals("456", ((Book) rs).getBook_ISBN()); assertEquals("计算机科学", ((Book) rs).getBook_category()); assertEquals("java编程思想", ((Book) rs).getBook_name()); assertEquals("张三", ((Book) rs).getBook_author()); assertEquals("机械工业出版社", ((Book) rs).getPublish_house()); assertEquals("2020-01",((Book) rs).getPublish_time()); assertEquals(65, ((Book) rs).getBook_price(), 0.01); assertEquals(12, ((Book) rs).getBook_sum()); assertEquals(4, ((Book) rs).getBook_remain()); assertEquals("无", ((Book) rs).getBook_introduce());会报错

2023-06-12 上传
assertEquals(4, book.getBook_remain()); assertEquals("无", book.getBook_introduce()); } ``` 注意，这里使用了if (rs.next())来判断是否查询到了结果，并且只取第一条结果作为Book对象。如果你需要查询多条...
死磕代码程序媛
  • 粉丝: 110
  • 资源: 315
上传资源 快速赚钱

最新资源