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R是一种用于统计计算和图形的编程语言，由R核心团队和R统计计算基金会支持。R由统计学家Ross Ihaka和Robert Gentleman创建，在数据挖掘者和统计学家中被用于数据分析和开发统计软件。用户已经创建了软件包来增强R语言的功能。

statistics-lab™ 为您的留学生涯保驾护航 在代写R语言方面已经树立了自己的口碑, 保证靠谱, 高质且原创的统计Statistics代写服务。我们的专家在代写R语言代写方面经验极为丰富，各种代写R语言相关的作业也就用不着说。

• 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|R语言代写R language代考|Data sets in $\mathrm{R}$ and packages

To be able to present more meaningful examples, we need some real data. Here we use cars, one of the many data sets included in base R. Function data() is used to load data objects that are included in $\mathrm{R}$ or contained in packages. It is also possible to import data saved in files with foreign formats, defined by other software or commonly used for data exchange. Package ‘foreign’, included in the R distribution, as well as contributed packages make available functions capable of reading and decoding various foreign formats. How to read or import “foreign” data is discussed in $\mathrm{R}$ documentation in $\mathrm{R}$ Data Import/Export, and in this book, in chapter 8 starting on page 293 . It is also good to keep in mind that in R, URLs (Uniform Resource Locators) are accepted as arguments to the file or path parameter of many functions (see section $8.12$ starting on page 322 ).

In the next example we load data included in $R$ as $R$ objects by calling function data(). The loaded $\mathrm{R}$ object cars is a data frame.
data (cars)
Once we have a data set available, the first step is usually to explore it, and we will do this with cars in section $2.17$ on page 81 .By default, at the end of a session, the current workspace containing the results of your work is saved into a file called . RData. In addition to saving the whole workspace, it is possible to save one or more R objects present in the workspace to disk using the same file format (with file name tag . rda or . Rda). One or more objects, belonging to any mode or class can be saved into a single file using function save( $)$. Reading the file restores all the saved objects into the current workspace with their original names. These files are portable across most $\mathrm{R}$ versions-i.e., old formats can be read and written by newer versions of $R$, although the newer, default format may be not readable with earlier $\mathrm{R}$ versions. Whether compression is used, and whether the “binary” data is encoded into ASCII characters, allowing maximum portability at the expense of increased size can be controlled by passing suitable arguments to save().

## 统计代写|R语言代写R language代考|Looking at data

There are several functions in $\mathrm{R}$ that let us obtain different views into objects. Function printo is useful for small data sets, or objects. Especially in the case of large data frames, we need to explore them step by step. In the case of named components, we can obtain their names with colnames (), rownames(), and names(). If a data frame contains many rows of observations, head( ) and tai1() allow us to easily restrict the number of rows printed. Functions nrow() and ncol () return the number of rows and columns in the data frame (also applicable to matrices but not to lists or vectors where we use length()). As mentioned earlier, function str() concisely displays the structure of R objects.

The different columns of a data frame can be factors or vectors of various modes (e.g., numeric, logical, character, etc.) (see section $2.14$ on page 66). To explore the mode of the columns of cars, we can use an apply function. In the present case, we want to apply function class() to each column of the data frame cars. (Apply functions are described in section $3.4$ on page 108 .)

The statement above returns a vector of character strings, with the mode of each column. Each element of the vector is named according to the name of the corresponding “column” in the data frame. For this same statement to be used with any other data frame or list, we need only to substitute the name of the object, the argument to the first parameter called $\mathrm{x}$, to the one of current interest.

# R语言代写

## 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。

assignmentutor™您的专属作业导师
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