### 统计代写|python代考|Treating a String Like a List

Python是一种高级的、解释性的、通用的编程语言。它的设计理念强调代码的可读性，使用大量的缩进。

Python是动态类型的，并且是垃圾收集的。它支持多种编程范式，包括结构化（特别是程序化）、面向对象和函数式编程。由于其全面的标准库，它经常被描述为一种 “包含电池 “的语言。

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• Statistical Inference 统计推断
• Statistical Computing 统计计算
• (Generalized) Linear Models 广义线性模型
• Statistical Machine Learning 统计机器学习
• Longitudinal Data Analysis 纵向数据分析
• Foundations of Data Science 数据科学基础

## 统计代写|python代考|Treating a String Like a List

Python offers an interesting feature of strings. Sometimes, it is useful to be able to treat a string as though it were a list of individual characters. It’s not uncommon to have extraneous characters at the end of a string. People may not recognize these, but computers will get hung up on them. It’s also common to only need to look at the first character of a string to know what you want to do with it. For instance, if you had a list of last names and first names, you could view the first letter of each by using the same syntax that you would for a list. This method of looking at strings is called slicing and is one of the fun things about Python:

$\Rightarrow>$ last_names = [ “Douglass”, “Jefferson”, “Williams”, “Frank”, “Thomas” ]

print “ofs” of last_names[0]
Douglass
$>>$ print “ofs” 항 last_names[0][0]
D
print ” o \$s” of last_names [1] Jefferson$>>>$print “o्os” of last_names [1] [0]$\Rightarrow>$print “ơos” 항 last_names [2] Williams print “o्षs” of last_names[2][0]$\mathrm{W}$print “o्8s” of last_names [3] Frank$>>>$print “o्ㅎ” 뭉 last_names [3] [0]$\mathrm{F}$print “o 와” 왕 last_names [4] Thomas print “oेs” of last_names[4][0]$\mathrm{T}$For example, you can use the letter positioning of strings to arrange them into groups in a dictionary based on the first letter of the last name. You don’t need to do anything complicated; you can just check to see which letter the string containing the name starts with and file it under that:$>>$by_letter$={1>>$by_letter[last_names [0] [0]] = last_names [0]$>>$by_letter [last_names [1][0]] = last_names [1]$>>$by_letter[last_names [2][0]] = last_names [2]$>>>$by_letter[1ast_names [3] [0]] = last_names [3]$>>$by_letter [last_names [5] [0]$=$last_names [5] The by_letter dictionary will, thanks to string slicing, only contain the first letter from each of the last names. Therefore, by_letter is a dictionary indexed by the first letter of each last name. You could also make each key in by_letter reference a list instead and use the append method of that list to create a list of names beginning with that letter (if, of course, you wanted to have a dictionary that indexed a larger group of names, where each one did not begin with a different letter). Remember that, like tuples, strings are immutable. When you are slicing strings, you are actually creating new strings that are copies of sections of the original string. ## 统计代写|python代考|Special Types There are a handful of special types in Python. You’ve seen them all, but they bear mentioning on their own: None, True, and False are all special built-in values that are useful at different times. None is special because there is only one None. It’s a name that no matter how many times you use it, it doesn’t match any other object, just itself. When you use functions that don’t have anything to return to you – that is, when the function doesn’t have anything to respond with – it will return None. True and False are special representations of the numbers 1 and 0 . This prevents a lot of the confusion that is common in other programming languages where the truth value of a statement is arbitrary. For instance, in a Unix shell (shell is both how you interact with the system, as well as a programming language), 0 is true and anything else is false. With$\mathrm{C}$and Perl, 0 is false and anything else is true. However, in all of these cases, there are no built-in names to distinguish these values. Python makes this easier by explicitly naming the values. The names True and False can be used in elementary comparisons, which you’ll see a lot; and in Chapter 4, you will learn how these comparisons can dramatically affect your programs – in fact, they enable you to make decisions within your program.$>>>$True True$\rightarrow>$False False$\Rightarrow>$True$==1$True$>>>$True True$>>>$False False$>>>$True$==1$True$>>>$True$==0$False$>>>$False$==1$False$>>>$False$==0$True$\Rightarrow>$True$==0$False ) False$==1$False$>>\Rightarrow$False$==0$True ## 统计代写|python代考|Referencing the Last Elements All of the sequence types provide you with some shortcuts to make their use more convenient. You often need to know the contents of the final element of a sequence, and you can get that information in two ways. One way is to get the number of elements in the list and then use that number to directly access the value there:$>>$last_names = [ “Douglass”, “Jefferson”, “Williams”, “Frank”, “Thomas” ]$>>>$len (last_names) 5$>>$last_element = 1en (last_names) – 1$\rightarrow>$print “o्8s” 훟 last_names[last_element] Thomas However, that method takes two steps; and as a programmer, typing it repeatedly in a program can be time-consuming. Fortunately, Python provides a shortcut that enables you to access the last element of a sequence by using the number$-1$, and the next-to-last element with$-2$, letting you reverse the order of the list by using negative numbers from$-1$to the number that is the negative length of the list (-5 in the case of the last_names list).$>>$print “ofo” of last_names$[-1]$Thomas$>>>$print “ofos” 핳 last_names$[-2]$Frank$>>$print “o्षेs” 형 last_names$[-3]$Williams ## python代写 ## 统计代写|python代考|Treating a String Like a List Python 提供了一个有趣的字符串特性。有时，能够将字符串视为单个字符的列表很有用。在字符串的末尾有多余的字符并不少见。人们可能无法识别这些，但计算机会挂断它们。只需要查看字符串的第一个字符就知道你想用它做什么也是很常见的。例如，如果您有一个姓氏和名字的列表，您可以使用与列表相同的语法来查看每个名字的第一个字母。这种查看字符串的方法称为切片，是 Python 的有趣之处之一： ⇒>last_names = [“道格拉斯”、“杰斐逊”、“威廉姆斯”、“弗兰克”、“托马斯”] 打印 last_names[0] Douglass的“ofs” >>打印“ofs” 항 last_names[0][0] D 打印“o$ s” of last_names [1]
Jefferson
>>>打印姓氏 [1] [0] 的“o्os”
⇒>打印“ơos” 항 last_names [2]

Frank
>>>打印“o्ha” Mung last_names [3] [0]
F

Thomas

>>by_letter $={1>>b是l和吨吨和r[l一种s吨n一种米和s[0][0]]=l一种s吨n一种米和s[0]>>b是l和吨吨和r[l一种s吨n一种米和s[1][0]]=l一种s吨n一种米和s[1]>>b是l和吨吨和r[l一种s吨n一种米和s[2][0]]=l一种s吨n一种米和s[2]>>>b是l和吨吨和r[1一种s吨n一种米和s[3][0]]=l一种s吨n一种米和s[3]>>b是l和吨吨和r[l一种s吨n一种米和s[5][0]=$ last_names [5]

## 统计代写|python代考|Special Types

Python中有一些特殊类型。您已经看到了它们，但它们本身值得一提：None、True 和 False 都是在不同时间有用的特殊内置值。

None 是特殊的，因为只有一个 None。这是一个名称，无论你使用多少次，它都不匹配任何其他对象，只匹配它自己。当你使用没有任何东西可以返回给你的函数时——也就是说，当函数没有任何东西可以响应时——它会返回 None。

True 和 False 是数字 1 和 0 的特殊表示。这避免了其他编程语言中常见的许多混淆，其中语句的真值是任意的。例如，在 Unix shell 中（shell 既是你与系统交互的方式，也是一种编程语言），0 为真，其他任何东西都是假的。和C和 Perl，0 是假的，其他的都是真的。但是，在所有这些情况下，都没有内置名称来区分这些值。Python 通过显式命名值使这更容易。名称 True 和 False 可用于基本比较，您会看到很多；在第 4 章中，您将了解这些比较如何极大地影响您的程序——事实上，它们使您能够在程序中做出决定。
>>>真真
_
→>假

⇒>真的==1

>>>真真
_
>>>假

>>>真的==1

>>>真的==0

>>>错误的==1

>>>错误的==0

⇒>真的==0

） 错误的==1

>>⇒错误的==0

## 统计代写|python代考|Referencing the Last Elements

>>last_names = [“道格拉斯”、“杰斐逊”、“威廉姆斯”、“弗兰克”、“托马斯”]
>>>len (last_names)
5
>>last_element = 1en (last_names) – 1
→>print “o्8s” 훟 last_names[last_element]
Thomas

>>打印姓氏的“ofo”[−1]

>>>打印“ofos” 핳 last_names[−2]

>>打印“o्षेs”형 last_names[−3]

## 有限元方法代写

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## MATLAB代写

MATLAB 是一种用于技术计算的高性能语言。它将计算、可视化和编程集成在一个易于使用的环境中，其中问题和解决方案以熟悉的数学符号表示。典型用途包括：数学和计算算法开发建模、仿真和原型制作数据分析、探索和可视化科学和工程图形应用程序开发，包括图形用户界面构建MATLAB 是一个交互式系统，其基本数据元素是一个不需要维度的数组。这使您可以解决许多技术计算问题，尤其是那些具有矩阵和向量公式的问题，而只需用 C 或 Fortran 等标量非交互式语言编写程序所需的时间的一小部分。MATLAB 名称代表矩阵实验室。MATLAB 最初的编写目的是提供对由 LINPACK 和 EISPACK 项目开发的矩阵软件的轻松访问，这两个项目共同代表了矩阵计算软件的最新技术。MATLAB 经过多年的发展，得到了许多用户的投入。在大学环境中，它是数学、工程和科学入门和高级课程的标准教学工具。在工业领域，MATLAB 是高效研究、开发和分析的首选工具。MATLAB 具有一系列称为工具箱的特定于应用程序的解决方案。对于大多数 MATLAB 用户来说非常重要，工具箱允许您学习应用专业技术。工具箱是 MATLAB 函数（M 文件）的综合集合，可扩展 MATLAB 环境以解决特定类别的问题。可用工具箱的领域包括信号处理、控制系统、神经网络、模糊逻辑、小波、仿真等。